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GIFT   OF 
MICHAEL  REESE 


CHEMISTRY 


OF  THE 


ORGANIC    DYESTUFFS. 


BY 


B,  NIETZKI,  PH.D., 

PROFESSOR    AT   THE    UNIVERSITY   OF    BASLE. 


TRANSLATED,    WITH  ADDITIONS,    BY 

A.  COLLIN,  PH.D.,  AND  W.  RICHARDSON. 


LONDON : 

GFRNEY   &   JACKSON,    1   PATERNOSTER    ROW. 

(SUCCESSORS  TO  MB.  VAN  VOORST.) 
MDCCCXCH. 


PRINTED    BY    TAYLOR    AND    FRANCIS, 
HBD  LION  COURT,  FLEET  STREET. 


AUTHOE'S    PREFACE. 


ABOUT  three  years  ago  I  wrote  an  article  for  Ladenburg's 
'  Handworterbuch  der  Chemie/  containing  in  a  concise  form  an 
exhaustive  account  of  the  history  of  the  Organic  Dyestuffs.  This 
article  was  also  published  separately,  and  its  good  reception 
induced  me  to  produce  the  present  work,  which  I  have  based  as 
far  as  possible  upon  the  earlier  one. 

The  article  in  question  was  not  complete  in  itself,  and  in  the 
present  instance  certain  sections  which  came  under  other  headings 
in  the  '  Handworterbuch '  have  been  added.  New  material  has 
also  been  supplied  through  the  advances  made  in  the  coal-tar 
colour  industry  and  in  our  scientific  knowledge  of  the  constitution 
of  dyestuffs  during  the  last  three  years.  Again,  some  subjects 
have  been  dealt  with  at  a  greater  length  than  was  permitted  by 
the  somewhat  limited  space  of  the  '  Handworterbuch/  Conse- 
quently, the  subject-matter  of  the  earlier  work  has  been  submitted 
to  a  thorough  revision,  and  the  systematic  classification  of  dye- 
stuffs  into  natural  chemical  groups  attempted  in  the  original  book 
has  been  carried  out  in  a  more  complete  manner,  owing  to  the 
advances  made  in  our  knowledge  of  their  constitution. 

The  present  work  cannot  therefore  be  regarded  as  a  second 
edition  of  the  article  from  the  '  Handworterbuch/  and  as  I  have 
sought  to  give  the  whole  the  form  of  a  small  chemical  handbook, 


vi  AUTHOR'S  PREFACE. 

dealing  with  dyestuffs  from  a  scientific  standpoint,  I  have  selected 
'  The  Chemistry  of  the  Organic  Dyestuffs '  as  a  suitable  title. 

In  this  work,  as  in  the  previous  one,  considerable  weight  has 
been  laid  upon  the  relationships  existent  between  the  constitution 
and  tinctorial  properties  of  the  dyestuffs. 

I  have  thought  it  advisable  to  deal  only  with  the  principles 
involved  in  the  manufacture  of  individual  dyestuffs,  as  details  for 
their  technical  production  are  unreliable,  owing  to  the  continuous 
developments  taking  place  in  the  industry  in  question. 

The  application  of  dyestuffs  to  textile  fibres  has  been  dealt  with 
rather  more  fully  than  in  the  earlier  work,  but  not  at  a  greater 
length  than  is  in  accordance  with  the  character  of  the  book.  To 
technologists  requiring  further  details  of  the  application  of  dye- 
stuffs  I  can  recommend  Hummers  excellent  work  on  '  The 
Dyeing  of  Textile  Fabrics/ 

Basle,  October  1888. 


TRANSLATORS'    PREFACE. 


LITTLE  remains  for  us  to  add  to  Prof.  Nietzki's  account  of  the 
design  and  character  of  his  book.  It  has  met  with  very  general 
appreciation  in  Germany,  and  this  made  us  think  that  a  trans- 
lation might  be  of  service  to  English  workers  in  the  field  which 
the  book  covers. 

Some  time  has  elapsed  since  the  original  appeared,  and  we  have 
attempted  as  far  as  possible  to  bring  the  subject-matter  up  to  date. 
New  colouring-matters  have  been  introduced  without  altering 
Prof.  Nietzki's  method  of  classification,  a  method  which  has  been 
very  generally  adopted  since  its  appearance.  In  some  cases 
(Primuline,  Thioflavine  ;  Pyronine,  &c.)  new  sections  might  have 
been  desirable ;  we  preferred,  however,  to  leave  the  book  in  its 
original  form. 

The  figures  in  the  text  apply  to  the  references  given  on  pages 
273-288.  The  references  have  been  left  as  in  the  original,  with 
the  one  exception  that,  wherever  possible,  the  English-Patent 
number  has  been  added. 

Our  thanks  are  due  to  the  Directors  of  the  Farbwerke  Hochst 
(Meister,  Lucius,  and  Briining)  and  of  the  Farbenfabriken,  vortnals 
F.  Bayer  and  Co.,  Elberfeld,  for  the  ready  kindness  with  which 
they  placed  ample  information  at  our  disposal. 

Paisley,  May  1892. 


CONTENTS. 


Page 

INTRODUCTION 1-22 

Colour,  1 ;  Chromophors,  Chromogens,  3 ;  Theory  of  dyeing,  4 ;  Con- 
stitution of  chromogens,  7;  Salt- forming  groups,  Auxochromic 
groups,  12 ;  Acid  and  basic  dyestuffs,  14 ;  Mordants,  lakes,  15 ; 
Dye-trials,  16 :  History  of  artificial  colours,  17 ;  Classification, 
22. 

CHAPTEE  I. 

NITRO-COMPOUNDS 23-27 

General,  23 ;  Picric  Acid  (Trinitrophenol),  24 ;  Dinitrocresol,  24 ; 
Dinitronaphthol,  Dinitronaphtholsulphonic  Acid,  25;  Brilliant 
Yellow,  Tetranitronaphthol,  Palatine  Orange,  Aurantia,  Salicyl 
Yellow,  26  ;  Isopurpuric  Acid,  27. 


CHAPTEE  II. 

AZO-DYESTTJEFS        28-79 

Introductory,  28-34. 

I.  AMIDOAZO-COMPOFNDS   35-43 

Amidoazobenzene,  35  ;  Amidoazobenzenemonosulphonic  Acid,  36 ; 
Amidoazobenzenedisulphonic  Acid  (Acid  Yellow),  36 ;  Dimethyl- 
amidoazobenzene,  Dimethylamidoazobenzenesulphonic  Acid,  37 ; 
Phenylamidoazobenzene,  Phenylamidoazobenzenesulphonic  Acid 
(Tropaolin  00),  38  ;  Amidoazotoluenebenzene,  Amidoazo- 
toluenes,  39  ;  Amidoazoxylenes,  40  ;  Diamidoazobenzene  (Chry- 
soidine),  40 ;  Parazoaniline,  41 ;  Triamidoazobenzene  (Bismark 
Brown),  42;  Benzeneamidoazonaphthalene,  Amidoazonaplitha- 
lene,  43. 


X  CONTENTS. 

Page 

II.  OXYAZO-COMPOUNDS  ...    44-59 

Oxyazobenzene,  Dioxyazobenzene,  44 ;  Tropaolin  0,  45 ;  Dioxyazo- 
benzenes  (Azophenols),  45. 

Naphtholazo-dyes,  constitution,  46 ;  Naphtholsulphonic  Acids,  48  ; 
Azobenzene-a-naphthol,  53 ;  Monosulphonic  Acid  (Orange  I), 
54 ;  Azobenzene-/3-naphthol,  Sulphonic  Acids,  54 ;  Disulphonic 
Acids,  Orange  G,  Crocei'n  Orange,  Scarlet  2  G,  55 ;  Azo-dyes 
from  /3-naphtholdisulphonic  acids,  55,  56  ;  a-azonaphthalene-j(3- 
naphthol,  Monosulphonic  Acid  (Roccellerie,  Fast  Bed),  57; 
Disulphonic  Acids,  Bordeaux  B,  Crystal  Scarlet,  Crocei'n  Scarlet 
3  Bx,  Azorubin,  58 ;  Silk-red,  59. 

III.  AZC-DYES  FROM  DlAZO-CARBONIC  ACIDS      59,  60 

Dimethylamidobenzeneazobenzoic  Acid,  Phenolazometabenzoic  Acid, 
Resorcinazobenzoic  Acid,  /3-naphtholazobenzoic  Acid,  59. 

IV.  AZO-DYES  FROM  CARBONIC  ACIDS  AND  DIAZO-COMPOUNDS    ....    (30-62 

Azobenzenedimethylamidobenzoic  Acid,  Dimethylamidobenzoic  Acid- 
azobenzoic  Acid,  Azo-3-diamidobenzoicacid-p-benzenesulphonic 
Acid,  60 ;  Azobenzenesalicylic  Acid,  Azonaphthalenesalicylic 
Acid,  Dyes  from  Nitrodiazo-compounds  and  Salicylic  Acid 
(Alizarin  Yellows),  61. 

V.  TETRAZO-  OR  DISAZO-DYESTUFFS 62-74 

Introductory,  Phenoldisazobenzene,  62 ;  Resorcinazobenzene,  63 ; 
Azo-dyes  from  Amidoazo-compounds,  63 ;  Benzenedisazobenzene- 
/3-naphthol,  Monosulphonic  and  Disulphonic  Acids,  Biebrich 
Scarlet,  64;  Crocein  Scarlets,  Archil  Brown,  Wool  Black,  65 ;  Azo- 
dibehzenephenylenediamine,  65 ;  Azodibenzene  toluylenediamine, 
66;  Table  of  dyes  from  Amidoazo-compounds,  66;  Secondary 
and  Tertiary  azo-dyes  from  Nitrodiazocompounds,  67. 

Azo-dyes  from  Benzidine  and  analogous  bases,  68-74. 

Congo  Red,  68 ;  Sulphonic  Acids  of  a.-  and  /3-naphthylamine,  69- 
70  ;  Azo-blue,  Benzazurine,  Tetrazostilbenedisulphonic  Acid, 
71 ;  Table  of  direct  dyes,  72,  73,  74 ;  Azarin  S,  San  Yellow, 
Thiotoluidines  (Primuline),  75 ;  Erica,  Thioflavine,  76  ;  Direct 
production  of  Azo-dyes  on  the  fibre,  77  ;  Diamine  Blacks,  79. 


CONTENTS. 


CHAPTER  III. 

Page 
OXYQTTINONES  AND  QlTlNONEOXIMES 80-95 

Introductory,  80  ;  Naphthazarin,  81. 

Anthraquinone-dyestuffs,  81-92. 

Alizarin,  82 ;  Constitution,  formation,  properties,  83 ;  Technical 
production,  84 ;  Application,  Turkey  Red.  86 ;  Mtroalizarin, 
87  ;  Trioxyanthraquinones,  Purpurin,  87 ;  Iso-  (Anthra*-)  pur- 
purin,  Flavopurpurin,  88;  Anthragallol,  Alizarin  Bordeaux 
and  Cyanines,  89 ;  Alizarin  Blue,  91 ;  Alizarin  Indigo-blue 
S  and  Green,  92  ;  Styrogallol,  92. 

Quinoneoximes,  93-95. 

Introductory,  Dinitrosoresorcin,  93 ;  Fast  Green,  94. 

Naphthaquinoneoximes,  94;  Gambine  R  &  G,  Naphthol  Green, 
Dioxine,  95.  . 


CHAPTER  IV. 
.  KETONEIHIDES  AND  HYDKAZIDES      96-101 

Introductory,  96 ;  Auramine,  preparation,  98;  salts,  properties, 
Phenyl-  and  Tolyl-auramine,  99  ;  Phenylhydrazides,  Tartrazine, 
100. 


CHAPTER  Y. 

TRIPHENYLMETHANE  DYESTUFFS    102-145 

Introductory,  102 ;  Formation,  104. 

A.  Rosaniline  Dyestuffs 105-131 

Tetramethyldiamidotriphenylcarbinol  (Malachite  Green),  106 ;  Salts, 
derivatives,  preparation,  107 ;  Nitro-derivative,  108 ;  Dichlorte- 
tramethyldiamidotriphenylcarbinol  (Victoria  Green  3  B), 
Tetraethyldiamidotriphenylcarbinol  (Yictoria  Green),  Sul- 
phonic  Acids,  Helvetia  Green,  109 ;  Light  Green  S,  Quinoline 
Green,  110;  Pararosaniline,  111;  Methyl  Violet,  112;  Manu- 


XU  CONTENTS. 

Page 

facture,  113;  Properties  and  composition,  Acid  Violets,  114; 
Hexamethylpararosaniline  (Crystal  Violet),  115  ;  Hexaethylpara- 
rosaniline  (Ethyl  Purple),  Azo-Green,  Methyl  Green,  116;  Rosani- 
line  Magenta),  118 ;  Formation,  119  ;  Base,  120  ;  Salts,  Sulphonic 
Acids  (Acid  Magenta),  Tetrabromrosaniline,  121 ;  Trimethyl-  and 
Tetramethylrosaniline,  Pentamethylrosaniline  (Iodine  Green), 
Hexamethylrosaniline,  122  ;  Triethylrosaniline  (Hofmann's 
Violet),  123;  Tetraethylrosaniline,  Acetyl,  Triacetyl-,  and 
Tribenzoylrosaniline,  123  ;  Magenta  residues,  123 ;  Aniline  Blue, 
124  ;  Manufacture,  125  ;  Monophenylrosaniline,  125  ;  Diphenyl- 
and  Triphenylrosaniline  (Aniline  Blue),  126 ;  Sulphonic  Acids 
of  Aniline  Blue,  Alkali  Blue,  Water  Blue,  Cotton  Blue,  126, 
127 ;  Diphenylamine  Blue,  128 ;  Aldehyde  Green,  128 ;  Di- 
phenylnaphthylmethane  dyestuffs,  Victoria  Blue  B,  130 ;  Night 
Blue,  131. 

B.  Rosolic  Add  Dyestuffs    131-135 

Introductory,  131 ;  Aurin  (Pararosolic  Acid),  Rosolic  Acid,  132 ; 
Pittacal,  Eupittonic  Acid,  133 ;  Hexamethoxylpararosaniline, 
134 ;  Aurintricarbonic  Acid  (Chrome  Violet),  134 ;  Dyestuffs 
from  Benzotrichloride  and  Phenols,  135;  Resorcin-benzein, 
Rosamines,  135. 

C.  Phthalems    . .  . , 136-143 

Constitution,  136 ;  Phenolphthale'm,  138  ;  Eluorescem,  Eosin,  139 ; 
Ethers  of  Eosin,  140 :  Spirit  Eosin,  Iodine  derivatives  of 
Fluorescem,  Lutecienne,  Erythrosine,  141 ;  Phloxiue,  Rose 
Bengal,  142;  Rhodamine,  142;  Pyronines,  143;  Gallem  and 
Cffirule'in,  144 ;  Glycerems,  145. 


CHAPTER  VI. 

QUINONEIMTDE  DYESTUFFS       * 146-168 

Introductory,  146. 

1.  Indamines    149-151 

Phenylene  Blue,  Tetramethylindamine,  149 ;  Toluylene  Blue,  150. 

2.  Indophenols     151-153 

Preparation,  properties,  151  ;  Application,  152. 


CONTENTS.  xiii 

Page 

3.  Indamines  and  Indophenols  containing  Sulphur   ....    153-161 
Introductory,    153;    Lauth's   Violet,    155;    Methylene  Blue,   155; 

Imidothiodiphenylimide,  158;  Thionolines,  Oxythiodiphenyl- 
imide,  Thionol,  159  ;  Methylene  Red,  160  ;  Methylene  Green,  161. 

4.  Oxyindamine  and  Oxyindophenols  (Oxazines)   161-165 

Naphthol  Blue  (Fast  Blue),  161 ;  Muscarine,  162  ;  Nile  Blue,  Gallo- 

cyanine,  163;  Gallamine  Blue,  164;  Prune,  165. 

5.  Dichroines 165-168 

Resorufin,  165;  Resazurine,  167:  Orcirufm,  168. 

CHAPTER  VII. 
AZINE  DYESTTTFFS 169-191 

Constitution  and  formation,  169. 

1.  Eurhodines  (Amido-azines)     172-174 

2.  Eurhodols  (Oxy-azines) 175 

3.  Toluylene  Red     175,  176 

Toluylene  Violet,  Neutral  Violet,  176. 

4.  Saffranines   177-189 

Introductory,  177  ;  Manufacture,  180  ;  Phenosaffranine,  181 ;  Diazo- 

compounds,  182;  a-  and  /3-dimethylphenosaffranine,  Tetrame- 
thylphenosaffranine,  Diethylsaffranines,  183 ;  Acetyl  and  diazo- 
compounds  of  Diethylsaffranines,  184;  Tetraethylphenosaffra- 
nine,  185 ;  Tolusaffranine,  185 ;  Methoxysaffranines,  186 ; 
Neutral  Blue,  187 ;  Saffranol,  187  ;  Itidazine  M,  Basle  Blue, 
188;  Azine  Green,  189. 

5.  Magdala  Red 189 

6.  Mauvei'ne     190,  191 

CHAPTER  VIII. 
ANILINE  BLACK     192-199 

Formation,    192;    Properties,   193;    Constitution,    194:    Technical 
Aniline  Black,  applications,  197. 

CHAPTER  IX. 

INDULINES  AND  NIGROSINES 200-206 

Formation,  200  ;  Azophenine,  201 ;  Indulines  B,  3  B,  and  6  B,  202 
Soluble  Indulines,  203 ;  Nigrosines,   204  r  Applications,  205  ; 
Rosindulmes,  Azocarmine,  205  ;  Fluorindines,  206. 


XIV  CONTEXTS. 

CHAPTER  X. 

QUINOLINE  AND  ACRIDINE  DYESTUFFS 207-218 

Cyanine,  Quinoline  Red,  208 ;  Quinoline  Yellow  (Quinophthalon), 
209;  Elavaniline,  210;  Berberine,  212;  Chrysaniline,  212; 
Salts  and  derivatives,  213;  Chrysophenol,  214;  Synthesis  of 
Chrysaniline,  214 ;  Acridine  Yellow,  Acridine  Orange,  Benzo- 
flavine,  216. 

CHAPTER  XL 

INDIGO  DYESTUFFS     219-241 

Indol,  219  ;  Indoxyl,  220;  Indoxylic  Acid,  Oxindol ;  Dioxindol, 
221 ;  Isatin,  222  ;  Isatic  Acid,  223  ;  Isatogenic  Ether,  Diisa- 
togen,  Indoxanthic  Ether,  Indigo  Blue,  224  ;  Preparation  and 
properties  of  Indigo-blue,  225  ;  Dibenzoyl-indigo,  Indigo-white, 
226 ;  Indigo- sulphonic  Acids,  227  ;  Application  of  Indigo  in 
dyeing,  228  ;  Indigo-dicarbonic  Acid,  Indoine,  229  ;  Indigo- 
purpurin,  Indirubin,  Indigo-red,  231. 

Synthesis  of  Indigo-blue      231-236 

Prom  Indol  and  from  Isatin,  231  ;  Orthonitrophenylpropiolic  Acid, 
232 ;  Synthesis  from  Orthonitrobenzaldehyde,  233 ;  from  Ben- 
zylidene-acetone,  234 ;  from  Bromacetanilide  and  from  Phenyl- 
glycocine,  235  ;  Synthesis  of  Indigo-disulphonic  Acid,  236. 

Constitution  of  the  Indigo-group    236-241 

CHAPTER  XII. 

EUXANTHIC  ACID  AND  GA  LLOFLAVINE 242-246 

Euxanthic  Acid,  Purree,  242 ;  Euxanthone,  243 ;  Derivatives  and 
constitution,  244. 

Synthetical  Oxyketone  Dyestuffs     245 

Trioxybenzophenone  (Alizarin  Yellow  A),  Grallacetophenone  (Ali- 
zarin Yellow  G),  245. 

Ellagic  Acid,  245 ;  Galloflavine,  246. 

CHAPTER  XIII. 
CANAMNE , , ,   247 


CONTENTS.  XV 


CHAPTER  XIV. 

Page 
MUREXIDE ...   248 


CHAPTER  XY. 

DrESTUFFS  OF  UNKNOWN  CONSTITUTION 249-271 

Introductory,  .249 ;  Hsematoxylin,  Hsematei'n,  251 ;  Brazilin,  252 ; 
Brazilem,  Morin,  253 ;  Young  Fustic,  Quercitrin,  254 ;  Quer- 
citin,  255 ;  Rutin,  Xanthorhamnin,  Rhamnetin,  256  :  Luteolin, 
257  ;  Bixin,  258  ;  Chrysin,  Curcumin,  259  ;  Carotin,  Orchil  and 
Litmus,  260  ;  Carthamin,  262 ;  Santalin,  263  ;  Alkannin,  263 ; 
Crocin  and  Crocetin,  Lokao  (Chinese  Green),  264;  Cochineal, 
265 ;  Carmine  Red,  266 ;  Carmine,  267 ;  Lac-dye,  269 ;  Tyrian 
Purple,  269;  Catechu,  270;  Cachou  de  Laval  (Fast  Grey), 
271. 

REFERENCES 273-288 

APPENDIX      289-306 

INDEX   .  .   307-313 


ERRATA. 


P.  9.     Phenazine  formula,  read 


instead  of 


P  41.     For  Symmetrical  Amidoazobenzene  read  Symmetrical  Diamidoazobenzene. 
P.  54,  line  22,  for  Tropaolin  OOO  No.  1  read  Tropaolin  OOO  No.  2. 
P.  134.     Formula  for  Chrome-Violet  should  be 

/CCH3(OH)COOH 
C-C6H3(OH)COOH 
|  \08 

o7 


instead  of 


/C,H,(OH)COOH 

OH— C-C6H,(OH)COOH 

\C6H3(OH)COOH 


P.  136.    Kosamine  formula  should  be 


C/CX-N(CH3)2 


CCH3N(CH3)2C1 


instead  of 


CCH3N(CH3)2 


INTRODUCTION. 


CERTAIN  chemical  bodies  possess  the  property  of  only  transmitting 
or  reflecting  certain  constituents  of  white  light,  while  the  others 
are  absorbed.  '  In  other  words,,  such  bodies  have  a  particular 
colour,  more  or  less  characteristic.  These  bodies  occur  amongst 
the  so-called  chemical  elements,  and  the  colour  of  the  same  element 
may  be  totally  different  according  to  the  form  and  state  of  aggre- 
gation under  which  it  is  observed.  Certain  elements  (e.  g.  chro- 
mium) always  form  coloured  compounds ;  with  others,  again, 
the  coloration  of  the  compounds  may  be  regarded  as  an  exception, 
and  if  not  caused  by  combination  with  a  colour-giving  element, 
depends  on  the  constitution  of  the  compound. 

Coloured  carbon  compounds  come  under  the  latter  classification. 

The  number  of  organic  compounds  containing,  besides  carbon, 
hydrogen,  oxygen,  and  nitrogen  is  very  large,  and  by  far  the  greater 
number  of  them  are  colourless.  On  the  other  hand,  some  compounds 
of  carbon  with  these  elements  possess  colour  which  far  surpasses 
that  of  any  other  element,  both  as  regards  intensity  and  character. 
"*  The  coloured  carbon  compounds  often  differ  little,  or  not  at  all,, 
from  the  colourless  ones  in  their  percentage  composition,  and  it  is 
this  fact  which  renders  it  certain  that  it  is  the  structure  of  the 
compounds  which  causes  in  one  case  colour,  in  the  other  none. 

In  the  life-processes  of  plants  and  animals  both  colourless  and 
coloured  carbon  compounds  are  formed,  and  the  latter  have  been 
employed  since  the  earliest  periods  as  dye-materials. 


2  INTRODUCTION. 

Natural  dyes  tuffs  have  for  many  years  been  the  subjects  of 
thorough  chemical  investigation,  but  their  study  has  afforded  little 
knowledge  as  to  the  general  nature  of  coloured  carbon  compounds ; 
and  it  is  only  since  dyestuffs  have  been  prepared  synthetically 
that  we  have  gradually  come  to  understand  the  constitution  of  the 
greater  number  of  these  bodies. 

Very  little  is  known  of  the  primary  cause  of  colour  in  such 
compounds,  but  our  knowledge  is  so  far  advanced  that  colour 
is  regarded  as  a  characteristic  property  of  whole  classes  of 
chemical  compounds ;  and  the  study  of  the  constitution  of  such 
compounds  has  shown  that  a  close  relationship  exists  between 
their  colour  and  their  chemical  structure. 

VA  study  of  the  carbon  compounds  shows  that  compounds  of 
carbon  with  one  or  with  several  elements  of  equal  valency  are  all 
colourless.  For  example,  all  hydrocarbons  are  colourless,  and 
derivatives  obtained  by  the  introduction  of  monatomic  elements 
are  also  colourless. 

-  Colour  in  coloured  compounds  depends  on  the  introduction  of 
compound  radicals,  mostly  polyvalent ;  but  at  the  same  time  a 
certain  building-up  of  carbon  atoms  in  the  molecule  is  necessary 
for  production  of  a  real  colouring-matter.  For  the  latter  reason, 
nearly  all  organic  dyestuffs  belong  to  the  aromatic  series,  and  are 
derivatives  of  benzene,  naphthalene,  anthracene,  or  quinoline. 
The  radicals  which  possess  this  power  of  producing  colour  in  a 
hydrocarbon  show  a  characteristic  behaviour  towards  nascent 
hydrogen. 

•*  Nascent  hydrogen  possesses  the  property  of  converting  coloured 
carbon  compounds  into  colourless  ones  with  greater  or  less  facility ; 
the  reaction  which  takes  place  may,  however,  be  widely  different 
in  various  cases.  The  nitro-group  is  converted  into  an  amido- 
group,  and  on  oxidation  the  nitro-group  cannot  be  reproduced. 
The  azo-group  is  converted  in  a  similar  manner  into  two  amido- 
groups,  but  as  an  intermediate  stage  of  the  reaction  hydrazo- 
com pounds  are  formed. 

These  hydrazo-compounds  may  be  regarded  as  types  of  a  class 
of  colourless  bodies,  termed  leuco-compounds.  A  large  number 


INTRODUCTION.  3 

of  dyestuffs  yield  these  leuco-compounds  on  reduction.  These 
new  bodies  mostly  contain  two  atoms  of  hydrogen  more  than  the 
dyestuffs,  and  are  converted  into  the  latter  on  oxidation. 

This  circumstance  was  made  a  subject  of  study  by  Graebe  and 
Liebermann  (Ber.  i.  p.  106)  ;  and  in  1867  a  theory  was  advanced 
assuming  the  presence  of  a  bond  between  the  colour-giving  groups 
in  dyestuffs  yielding  leuco-compounds,  corresponding  to  the  linkage 
of  the  oxygen  atoms  in  quinone  in  the  constitutional  formula 
accepted  at  that  period.  In  1876  Otto  N.  Witt  published  a  more 
complete  theory  of  the  nature  of  colouring-matters,  and  this 
theory  may  be  comprised  in  the  following  general  laws  (Ber.  ix. 
p.  522). 

^  The  colour  of  a  compound  depends  on  the  presence  of  a  certain 
group  of  atoms,  which  is  therefore  termed  a  colour-giving  group 
or  chromophor. 

v  The  introduction  of  this  chromophor  produces  a  more  or  less 
intensely  coloured  body,  which,  however,  is  not  a  dyestuff;  and 
the  dyestuffs  are  only  formed  by  introduction  of  one  or  more 
radicals  capable  of  imparting  salt-forming  properties,  which  may 
be  acid  or  basic.  Witt  terms  compounds  which  only  contain  a 
chromophor,  chromogens. 

Before  proceeding  it  is  necessary,  however,  to  define  the  differ- 
ence between  a  coloured  body  and  a  dyestuff  somewhat  more 
clearly.  'A  real  dyestuff  is  a  body  which  possesses,  besides  colour, 
the  property  of  communicating  colour  to  fibres,  especially  to 
animal  fibres,  doing  this  by  reason  of  a  certain  peculiar  affinity 
betwixt  the  colouring-matter  and  the  fibre.  If  a  silk  skein  is 
placed  in  a  solution  of  dyestuff,  it  gradually  becomes  dyed,  while 
the  liquid,  if  not  too  concentrated,  finally  loses  the  whole  of  its 
colour. 

7  The  property  of  dyeing  belongs  principally  to  compounds 
possessing  a  more  or  less  marked  acid  or  basic  character.  It  is 
probable  that  these  properties  depend,  at  least  in  many  cases,  on 
a  partly  basic,  partly  acid  character  inherent  in  the  fibre,  which 
in  the  one  case  is  developed  by  the  colour- acid  and  in  tjie  other  by 
the  colour-base. 

B2 


4  INTRODUCTION. 

The  exact  relationship  between  a  fibre  and  a  dyestuff  is  not 

exactly  known.     Dyeing  processes  are  usually  divided  into  two 

1) categories :  adjective,  where  the  use  of  a  mordant  is  necessary,, 

^\nd  substantive,  where  no  third  body  is  required  to  fix  the  dyestuff 

jbn  the  fibre. 

Two  theories  as  to  the  nature  of  substantive  dyeing  have  been 
advanced,  a  chemical  and  a  mechanical  theory. 

The  chemical  theory  of  dyeing  supposes  that  a  chemical  com- 
bination of  dyestuff  and  fibre  takes  place,  and  this  view  is,  to  a 
certain  extent,  supported  by  experimental  proof,  the  researches  of 
Knecht  in  this  direction  being  especially  worthy  of  attention. 

According  to  the  nature  of  a  dyestuff,  the  fibre  may  act  the 
part  of  an  acid  or  of  a  base  :  thus  dyed  fibres  are  compounds  of 
fibre  and  dyestuff  constituted  like  salts. 

4  For  example,  rosaniline  is  a  colourless  base,  forming  red  salts. 
If  a  skein  of  wool  or  silk  be  warmed  in  a  colourless  solution  of 
rosaniline,  it  becomes  dyed  red,  and  as  completely  as  if  a  corre- 
sponding amount  of  a  salt  of  rosaniline  had  been  employed.  This 
behaviour  is  easily  explained  if  we  assume  that  the  fibre  plays 
the  part  of  an  acid,  combining  with  the  rosaniline  to  form  a  salt 
which,  like  rosaniline  salts,  has  a  red  colour.  It  may,  however,  be 
observed  that  the  red  colour  of  rosaniline  salts  is  only  evident  in 
solution,  and  in  the  solid  state  these  compounds  have  a  more  or 
less  marked  bronze-green  appearance.  This  point  has  been  raised 
by  upholders  of  other  theories,  that  were  a  salt  of  rosaniline  and 
fibre  formed,  it  might  naturally  be  expected  to  possess  the  green 
-  colour  of  the  solid  salts  of  rosaniline. 

If  we  regard  dyeing  operations  as  chemical  processes,  it  is 
probable,  in  applying  salts  of  colour-bases,  that  these  salts  are 
decomposed  in  the  dyeing  process,  the  fibre  combining  with  the 
base  and  the  acid  being  set  at  liberty.  Certain  strong  basic  dye- 
stuffs,  such  as  methyl  green,  which  (like  all  ammonium  bases) 
forms  very  stable  salts,  are  not  capable  of  dyeing  wool  directly.  If, 
however,  ammonia  is  added  to  the  dye-bath,  the  liberated  colour- 
base  combines  with  the  wool  and  dyes  it  green.  Silk,  on  the  other 
hand,  evidently  possesses  a  stronger  acid  character  than  wool,  as 


INTRODUCTION.  5 

it  may  be  dyed  with  methyl  green  without  any  assistance.  Knecht 
has  demonstrated  by  quantitative  experiments  that  in  dyeing  wool 
with  the  salts  of  basic  colours,  the  acid  in  combination  with  the 
colour-base  is  liberated  during  the  dyeing  process.  For  example, 
if  a  solution  of  rosaniline  hydrochloride  (magenta)  is  treated  with 
wool  till  all  colour  is  extracted,  the  hydrochloric  acid  which  was 
in  combination  with  the  rosaniline  remains  in  the  colourless  bath. 

The  behaviour  of  some  acid  dyestuffs  also  supports  the  chemical 
theory  of  dyeing. 

As  a  rule  animal  fibres  are  not  capable  of  decomposing  the 
salts  of  acid  dyestuffs,  and  in  dyeing  the  colour-acids  have  to  be 
set  at  liberty  by  the  addition  of  a  stronger  acid  to  the  dye-bath. 
Certain  colour- acids,  for  example  the  sulphonic  acids  of  amidoazo- 
compounds,  have  a  different  colour  to  that  of  their  alkali  salts.  In 
dyeing  wool  with  such  colour-acids,  the  shade  produced  is  that  of 
the  salts  and  not  that  of  the  colour-acid,  so  that  in  such  cases 
wool  evidently  plays  the  role  of  a  base. 

In  certain  cases  also  there  is  evidence  which  points  to  the  fact 
that  definite  molecular  combinations  of  dyestuff  and  fibre  exist. 

In  dyeing  processes,  from  a  practical  standpoint,  a  certain 
quantity  of  dyestuff,  seldom  exceeding  two  per  cent,  of  the  weight 
of  the  fibre,  is  found  necessary  to  produce  a  maximum  effect  as  far 
as  shade  is  concerned.  But  this  by  no  means  expresses  the  limit 
to  the  amount  of  dyestuff  which  may  be  taken  up  by  the  fibre,  as 
Knecht  has  found  that  wool  is  capable  of  extracting  far  larger 
quantities  from  concentrated  dye-baths.  If  a  calculation  be  made 
based  on  the  amount  of  picric  acid  which  is  taken  up  by  the  fibre, 
it.  is  found  that  the  maximum  amounts  of  naphthol  yellow  S, 
tartraziiie,  and  crystal  violet  which  may  be  combined  with  wool 
closely  approximate  to  molecular  quantities. 

Another  conclusion  which  follows  from  the  researches  of  the 
same  chemist,  is  that  many  cases  of  so-called  substantive  dyeing 
are  in  reality  adjective.  In  the  case  of  wool,  for  example,  a  com- 
pound has  been  isolated,  called  lanuguinic  acid,  and  it  has  been 
found  that  this  acid  is  capable  of  entering  into  combination  with 
dyestuffs,  producing  compounds  which,  although  amorphous,  closely 


6  INTRODUCTION. 

resemble  dyed  wool  in  their  properties.  It  is  possible  that  in 
dyeing  wool  the  action  of  boiling  water  liberates  this  substance, 
which  then  effects  the  combination  with  the  dyestuffs.  In  this 
hypothesis,  the  lanuguinic  acid  is  supposed  to  be  retained  in  the  fibre 
in  a  state  of  solid  solution. 

A  theory  of  solid  solution  has  been  applied  in  a  somewhat 
different  form  by  Witt  to  the  substantive  dyeing  of  wool,  silk,  and 
cotton.  A  skein  of  silk  dyed  with  magenta  is  according  to  the 
chemical  theory  a  combination  of  magenta  and  silk,  and  it  requires 
pretty  strong  soaping  to  remove  the  dye.  But  if  the  silk  be  treated 
with  alcohol,  which  is  certainly  capable  of  exerting  only  a  solvent 
effect,  all  the  colouring-matter  is  quickly  removed.  If  water  is 
added  to  the  alcoholic  solution,  the  dyestuff,  however,  returns  to 
the  silk.  This  behaviour,  unexplained  by  the  chemical  theory  of 
dyeing,  may  be  cleared  up  by  the  "solid  solution"  theory.  In 
this  especial  instance  of  silk  and  magenta,  we  must  suppose  that 
the  essential  constituent  of  the  silk  fibre,  fibroin,  has  a  greater 
solvent  action  for  magenta  than  water,  and  thus  withdraws  it 
from  its  aqueous  solution.  Alcohol  having  a  greater  solvent 
power  than  the  fibroin,  removes  the  dyestulf  from  the  fibre. 
Similar  cases  are  frequent  in  purely  chemical  operations,  and  the 
extraction  of  magenta  from  its  aqueous  solution  by  silk  is  exactly 
similar  to  the  removal  of  resorcin  from  an  aqueous  solution  by 
ether. 

The  different  behaviour  of  various  textile  fibres  in  dyeing  may 
be  explained  by  an  assumption  of  different  solvent  power ;  thus, 
silk  dyes  more  readily  than  other  fibres  because  the  fibroin  has  a 
greater  solvent  power.  Keratine  again,  the  principle  of  the  wool 
fibre,  possesses  a  greater  solvent  power  than  cellulose,  which  is 
only  capable  of  attracting  and  holding  in  solution  a  few  dyestuffs, 
such  as  the  tetrazo-dyes  of  the  benzidine  series,  and  in  certain 
cases  in  this  class  the  solvent  power  of  the  water  in  the  dye-bath 
has  tu  be  decreased  by  addition  of  salt. 

The  mechanical  theory  of  dyeing  is  based  on  the  assumption  that 
the  molecules  of  colouring-matter  leave  the  dye-bath  and  are 
mechanically  deposited  between  the  molecules  of  the  fibre. 

Certain  plant-fibres — for  example  jute,  the  bast-fibre  of  Cor- 


INTRODUCTION.  7 

chorus — have  the  property  of  fixing  dyestuffs  directly,  this  being 
due  to  the  presence  of  an  incrustation  of  foreign  matter,  present  on 
the  fibre. 

Many  amorphous  substances,  amongst  which  may  be  mentioned 
precipitated  sulphur,  gelatinous  silica,  and  Kieselguhr,  have  the 
power  of  attracting  basic  dyestuffs. 

The  properties  of  the  so-called  oxycellulose  are  also  of  interest 
from  a  tinctorial  standpoint.  On  oxidation  of  vegetable  fibre 
(cellulose)  with  chlorine,  chromic  acid,  or  similar  agents,  it  under- 
goes a  change,  and  becomes  capable  of  fixing  basic  dyestuffs  without 
a  mordant. 

A  consideration  of  the  radicals  capable  of  acting  as  chromophors 
shows  that  only  two  of  these,  the  nitro-  and  nitroso-groups,  are 
monatomic.  If  these  groups  are  introduced  alone  into  a  hydrocar- 
bon, the  body  produced  possesses  scarcely  any  colour.  A  coloured 
body  is  formed  if  a  salt-forming  group  be  also  introduced,  the 
latter  probably  forming  a  closed  ring  with  the  chromophor.  The 
case  is  similar  when  a  valent  chromophor  is  introduced  into 
several  hydrocarbons,  so  that  each  valency  is  attached  to  a  hydro- 
carbon group  not  in  linkage  with  any  other.  This  is  the  case  with 
the  ketones,  while  the  diketones  (quinones)  and  simple  ketones 
possessing  a  ring  constitution  (diphenylene  ketone)  are  coloured 
compounds. 

Azobenzene  forms  an  apparent  exception  to  this  rule  (see 
below) . 

The  ketone  group,  especially  when  it  occurs  twice,  as  in  the 
quinones,  is  one  of  the  most  important  chromophors.  The  oxygen 
atom  of  the  ketone  group  may  be  replaced  by  another  diatomic 
radical,  such  as  sulphur ;  or  the  ketone  carbon  atom  may  enter 
into  combination  with  two  valencies  of  a  diatomic  nitrogen  atom  : 
the  resulting  groups  C=S  and  C=N  in  general  possess  increased 
chromophoric  properties.  As  an  example  of  this,  it  may  be 
remarked  that  the  derivatives  of  simple  ketones  are  colourless, 
those  of  the  thioketones,  ketone-imides,  and  hydrazides  being 
coloured. 

The  ketone  group  C=O  appears  only  to  act  as  a  chromophor  when 
it  occurs  as  a  member  of  a  closed  ring  of  carbon  atoms.  A  large 


8 


INTRODUCTION. 


number  of  dyestuffs  may  be  regarded  as  built  up  similarly  to  the 
di-ketones  (ortho-  and  para-quinones)  ;  and  as  the  present  view 
of  the  constitution  of  the  quinones  is  expressed  by  the  following 
formula,  the  formula?  of  a  large  number  of  dyestuffs  have  to  be 
modified  accordingly. 
O 


O  Quinone. 

The  indamines  are  derivatives  of  quinone-imide,  and  accordingly 
a  change  from  a  tertiary  to  a  secondary  carbon  atom  must  be 
accepted  in  the  constitutional  formulae  of  these  bodies. 


NH 


N-C6H4— NH 


NH 

Quinone- iinide 
(unknown). 


NH 

Indamine. 


C6H4— NH2 


A   similar   constitution   may   be   accepted  for  rosaniline   and 
rosolic  acid. 

C=(C6H4NH2)2  C=(C6H4OH)2 


NH 

Rosaniline. 


0 
Rosolic  acid. 


INTRODUCTION. 


In  these  cases  the  oxygen  of  the  ketone  group  is  replaced  by  a 
diatomic  methane  rest. 

A  class  of  bodies  closely  resembling  the  paraquinones  are  the 
orthoquinones,  for  example  /3-naphthaquinone  and  phenan- 
threnequinone  are  members  of  this  class  of  compounds.  From 
these  a  new  class  of  compounds  may  be  obtained,  and  these  bodies, 
the  azines,  are  in  some  respects  analogous  to  the  paraquinones. 

If  an  orthodiamine  interacts  with  an  orthoquinone,  the  oxygen 
atoms  of  the  latter  are  eliminated,  and  tertiary  nitrogen  atoms 
enter  in  their  places,  a  new  ring  containing  two  nitrogen  atoms 
and  four  carbon  atoms  being  formed.  The  similarity  of  this  ring 
to  the  paraquinone  ring  exists  in  the  fact  that  in  the  former  tertiary 
nitrogen  atoms  take  the  place  of  the  chromophoric  C=O  groups  of 
the  latter. 

This  analogy  is  especially  marked  if  the  constitutional  formula  of 
anthraquinone  is  compared  with  that  of  the  simplest  aromatic  azine. 
CO  N 


CO 

Anthraquinone. 


N 
Phenazine. 


There  are  also  certain  points  of  resemblance  between  the  azines 
and  quinoline  and  acridine :  here  only  one  carbon  atom  is  re- 
placed by  nitrogen,  and  it  is  probably  owing  to  this  that  the 
chromogenic  nature  of  these  bodies  is  not  so  strongly  marked  as 
that  of  the  azines. 

N  N 


10 


INTRODUCTION. 


Generally  speaking,  the  introduction  of  the  simplest  chromo- 
phors  gives  rise  to  yellow  dyestuffs,  and  when  stronger  and  more 
complex  groups  are  introduced  the  colour  changes  through  red 
to  blue  &c.  For  example,  all  quinoline  and  acridine  dyestuffs 
are  yellow,  while  only  the  simplest  azines  have  this  colour  and 
become  red  and  blue  by  introduction  of  salt-forming  groups. 

In  some  other  dyestuffs  the  presence  of  the  lactone  ring 
C=O — O —  is  assumed,  and  here  again  the  oxygen  atom  may 
be  replaced  by  a  primary  nitrogen  atom  (indigo  dyestuffs) . 

It  will  be  noticed,  on  examining  the  constitution  of  the  chromo- 
gens  already  treated  of,  that  most  of  them  contain  the  chromo- 
phor  as  member  of  a  closed  ring,  differing  from  the  other 
members  in  valency  and  linkage. 

For  instance,  compounds  constituted  on  the  quinone  type 
contain  two  secondary  and  four  tertiary  carbon  atoms.  In  cases 
where  four  secondary  carbon  atoms  are  present,  as  in  rhodizonic 
acid,  C6(OH)2O4,  the  body  is  still  coloured;  but  if  all  the  six 
carbon  atoms  of  benzene  become  secondary,  as  in  triquinoyl  or 
perquinone,  C6O6,  the  colour  disappears*.  The  same  occurs  if  all 
the  carbon  atoms  of  quinone  become  tertiary,  i.  e.  by  reduction  of 
the  quinone  to  hydroquinone. 

An  attempt  to  explain  the  colours  of  all  carbon  compounds 
by  the  existence  of  such  rings  possesses  great  interest,  but  it  cannot 
be  denied  that  the  necessary  conditions  are  absent  in  numerous 
dyestuffs,  for  example,  thioketones,  ketone-imides,  and  hydrazides 
are  such  bodies,  i.  e.  tetramethyldiamidothiobenzophenone  and 
auramine, 

(CH3)2  N-C6H4-C-C6H4— N(CH3)2, 
II 
S 

(CH3)2-N— C6H4-C— C6H4-N(CH3)2, 

II 
NH 

in  which  the  chromophors  CS  and  CNH  are  not  present  as  a  ring 
but  as  an  open  chain. 

*  The  researches  of  Hantsch  (Ber.  xx.)  make  it  improbable  that  the  absence 
of  colour  in  triquinoyl  and  leuconic  acid  is  due  to  hydration. 


INTRODUCTION.  11 

The  nitre-compounds,  which  are  almost  the  only  class  in  which 
a  monatomic  group  acts  as  chromophor,  would  also  be  difficult  to 
bring  under  the  above  ring  classification.  There  is  no  doubt, 
however,  that  in  amido-  and  hydroxyl  derivatives  of  nitro-bodies 
there  is  a  certain  relationship  between  the  nitro-group  and  the 
hydroxyl  or  amido-group.  It  is  not  improbable  that  the  nitro- 
phenols  possess  a  similar  constitution  to  the  nitrosophenols,  which 
are  now  generally  regarded  as  quinoneoximes.  v  The  azo-dye- 
stuffs  are  a  class  of  bodies  the  properties  of  which  are  not  in 
accordance  with  their  constitution,  and  this  is  especially  marked 
in  the  first  member  of  the  series,  azobenzene. 

If  a  single  hydrogen  atom  in  a  benzene  ring  is  substituted,  or  if 
two  rings  are  joined  together  by  a  diatomic  radical,  the  bodies 
formed  are  colourless  or  only  slightly  coloured,  while  azobenzene 
is  an  intensely  coloured  compound  and  a  powerful  chromogen. 

This  leads  to  the  supposition  that  azobenzene  does  not  act 
according  to  the  simple  constitutional  formula  C6H5N=NC6H5 
in  certain  cases,  and  other  facts  tend  to  speculation  as  to  a 
more  complex  formula. 

Azobenzene  and  its  derivative  hydrazobenzene  may  be  con- 
verted into  a  derivative  of  diphenyl,  benzidine;  and  the  ease  with 
which  this  reaction  takes  place  seems  to  point  to  the  existence  of 
an  unstable  linkage  between  the  benzene  rings.  This  would  be 
most  readily  explained  by  the  assumption  that  a  change  in  the 
linkage  (from  double  to  single)  between  the  carbon  atoms  in  the 
benzene  chain  takes  place  in  a  similar  manner  to  the  linkage  in  the 
quinone  formula. 

The  following  formula  would  then  express  the  constitution  of 
azobenzene  : — 

N N 


12  INTRODUCTION. 

Naturally  such  formulae  are  hypothetical,  and  only  of  interest  in 
attempting  to  regard  all  dyestuffs  as  variations  of  a  common 
system. 

A  characteristic  of  the  radicals  which  act  as  chromophors  is 
that  they  are  never  perfectly  neutral  groups,  or  in  other  words 
their  introduction  confers  a  certain  tendency  towards  basic  or  acid 
properties  to  the  bodies  which  they  enter. 

By  introduction  of  salt-forming  groups  these  properties  become 
strengthened  in  one  or  other  of  these  directions.  According  to 
their  nature,  therefore,  these  chromophors  may  be  classified  as 
basic  or  acid-forming.  The  quinone  group,  for  example,  possesses 
strong  acid -forming  properties.  A  simple  hydroxyl  derivative 
of  a  hydrocarbon  possesses  weak  acid  properties,  while  the  hy- 
droxyl derivatives  of  the  quinones  have  these  properties  in  a  far 
higher  degree.  The  nitro-group  acts  similarly.  Chromophors 
which  contain  nitrogen  without  oxygen  tend  to  form  bases. 

We  have  still  to  consider  more  closely  the  nature  of  the  salt- 
forming  groups  which  have  already  been  mentioned. 

These  groups  may  act  totally  differently,  and  are  divided  into 
two  sharply  defined  classes. 

Certain  radicals,  generally  acid,  such  as  the  sulpho-group, 
SO3H,  and  the  carboxyl  group,  if  introduced  into  a  chromogen, 
confer  upon  it  acid  properties,  but  without  increasing  the  colour 
appreciably,  indeed  in  many  cases  the  dyeing  power  is  considerably 
decreased. 

Such  bodies  act  as  acid  dyestuffs,  and  the  group  introduced 
effects  the  combination  with  the  fibre. 

Azobenzene,  for  example,  has  no  affinity  for  animal  fibres,  being 
perfectly  neutral,  while  its  sulphonic  and  carbonic  acids  act  as 
weak  dyestuffs.  The  influence  of  amido-  and  hydroxyl  groups  is 
a  totally  different  one. 

By  introduction  of  these  radicals  the  chromogen  acquires  basic 
or  acid  properties,  and  at  the  same  time  a  considerable  modifica- 
tion in  the  colour  of  the  body  is  produced.  The  colour  generally 
becomes  more  intense;  in  many  cases  colour  is  only  produced 
when  these  groups  enter.  Having  regard  to  these  facts  the 
groups  (sulpho-  and  carboxyl)  may  be  termed  "  salt-forming/' 


INTRODUCTION.  13 

while   for    the   latter   Witt    has    recently   suggested   the   name 
auxochromic  (Ber.  xxi.  p.  325). 

The  relationship  existing  between  these  groups  and  the  chro- 
mophors  is  not  yet  explained.  In  the  case  of  the  oxyquinones 
it  has  already  been  pointed  out  that  the  chromophoric  quinone 
group  confers  strong  acid  properties  on  the  auxochromic  hydro- 
xyl  group.  The  same  is  also  observed  in  the  phthalei'ns  and 
rosolic-acid  dyestuffs.  These  hydroxyl  groups  play  at  the  same 
time  the  part  of  salt-formers,  and  produce  the  necessary  affinity 
for  the  fibre.  The  auxochromic  amido-groups  exert  a  somewhat 
different  influence  on  the  base-forming  amido-groups.  This 
behaviour  may  easily  be  explained  by  studying  the  basic  triphenyl- 
methaiie  dyestuffs,  for  instance  rosaniline.  Ilosaniline  contains, 
besides  the  chromophor  =C=R=NH,  two  auxochromic  amido- 
groups. 

It  is  certain  that  the  imide  group  of  this  chromophor 
combines  with  the  acid  in  the  formation  of  the  red  monoacid 
rosaniline  salts,  and  it  is  by  its  means  that  the  combination  with 
the  fibre  is  effected.  The  latter  is  deduced  from  the  fact  that 
rosaniline  dyes  the  colour  of  these  salts,  while  the  salts  formed 
by  neutralising  the  two  amido-groups  are  yellow. 

The  amidoazines  show  this  characteristic  in  a  somewhat  more 
striking  manner.  The  azines  contain  the  chromophor  : — 

N 


N 

and  the  simplest  members  of  the  series  are  weak  bases  forming 
salts  which  are  mostly  red  or  violet  and  only  stable  in  presence  of 
an  excess  of  acid. 

The  amidoazines,  for  example  toluylene  red  (diamidoazine),  are 
strong  bases  forming  red  monoacid  salts,  which,  however,  are  stable. 

Here  also  the  acid  radical  is  combined  with  the  azine  group, 
and  the  amido-groups  only  form  salts  in  presence  of  an  excess  of 
acid,  the  change  being  accompanied  by  a  characteristic  change  of 
colour  through  blue  to  green. 


14  INTRODUCTION. 

In  dyeing,  toluylene  red  produces  a  red  shade,  and  not  a  blue 
or  green,  so  that  the  azine  group  alone  enters  into  combination 
with  the  fibre. 

'It  is  easily  seen  that  in  these  cases  the  auxochromic  amido- 
groups  tend  to  strengthen  the  basic  character  of  the  chromophor, 
but  do  not  act  as  salt-formers.  At  the  same  time  the  colour 
becomes  more  intense.  According  to  a  rule  which  has  been  laid 
down  by  Witt,  the  stronger  of  two  similar  dyestuffs  is  always  that 
which  possesses  salt-forming  properties  in  a  higher  degree. 

From  this  it  may  be  conceived  that  the  simultaneous  presence 
of  a  basic  auxochromic  group  and  an  acid-forming  chromophor,  or 
vice  versa,  gives  rise  to  a  weak  dyestuff.  The  nitranilines  form  a 
case  in  point ;  they  are  weak  dyestuffs,  while  on  the  other  hana 
the  nitrophenols  have  tinctorial  properties  much  more  fully 
developed. 

^  From  the  foregoing  reasons  actual   dyestuffs  are  divided  into 
two  principal  classes — acid  and  basic. 

Certain  coloured  bodies  like  indigo  are  neutral,  and  possess  no 
affinity  for  textile  fibres.  Their  dyeing  is  effected  by  precipitating 
on  the  fibre  from  a  solution  as  in  vat  dyeing,  or  by  converting 
into  a  sulphonic  acid,  and  thereby  producing  a  capability  to  form 
salts. 

The  salts  of  certain  azosulphonic  acids  may  be  termed  neutral 
dyestuffs.  They  may  be  directly  fixed  on  vegetable  fibres. 
v  Most  basic  and  acid  dyestuffs  are  fixed  without  aid  by  animal 
fibres ;  vegetable  fibres,  on  the  other  hand,  require  the  interven- 
tion of  a  special  mordant.  Tannic  acid  is  generally  used  along 
with  basic  dyestuffs,  as  it  forms  insoluble  salts  with  these  com- 
pounds. 

Cotton  possesses  the  power  of  attracting  a  certain  amount  of 
tannic  acid  from  solutions  containing  this  body,  and  of  retaining 
it  even  after  washing.  Cotton  prepared  in  this  manner  may  be 
dyed  with  most  basic  dyestuffs  just  as  well  as  wool.  In  practice 
the  cotton  treated  with  tannic  acid  is  further  submitted  to  the 
action  of  tartar  emetic  or  some  other  antimony  compound.  An 
insoluble  salt  of  tannic  acid  and  antimony  oxide  is  formed,  and 


INTRODUCTION.  15 

this  fixes  basic  dyestuffs  with  the  greatest  ease.  The  advantage 
of  the  latter  method  is  that  the  shades  produced  are  faster  to 
soap.  Some  acid  dyestuffs  combine  with  metallic  oxides,  pro- 
ducing insoluble  lakes,  different  in  colour  to  the  original  dyestuffs, 
and  varying  considerably  with  the  metallic  oxide  used.  This 
property  is  much  used  to  effect  the  fixation  of  dyestuffs  on  the 
fibre,  especially  on  cotton.  Anthraquinone  derivatives  are  always 
fixed  in  this  manner,  and  numerous  natural  dyestuffs  also. 

This  peculiar  property  of  dyeing  on  metallic  mordants  has  as 
yet  had  no  satisfactory  explanation.  If  cotton  mordanted  with 
alumina  or  oxide  of  iron  is  placed  in  an  alizarin  bath,  the  lake  is 
precipitated  and  enters  into  intimate  combination  with  the  fibre. 

Many  dyestuffs  form  insoluble  lakes  with  metallic  oxides,  but 
the  property  of  combining  with  mordants  on  the  fibre  is  peculiar 
to  a  fe^.  Insoluble  lakes  may  be  obtained  from  the  cosines  and 
from  all  oxyanthraquinones,  but  the  former  class  of  bodies  can- 
not be  fixed  on  mordants,  and  of  the  latter  only  derivatives  o£ 
alizarin  possess  this  property. 

It  is  necessary  that  the  lake  produced  forms  a  certain  combina- 
tion with  the  fibre ;  if  not,  it  is  only  retained  superficially,  and  is 
removed  mechanically  during  the  dyeing  process.  It  has  been 
found  that  this  capability  of  dyeing  on  mordants  stands  in  close 
relationship  to  the  constitution  of  the  colouring-matter,  and  more 
especially  to  the  relative  positions  of  the  substituting  groups 
(compare  quinone  dyestuffs). 

The  commercial  value  of  a  colouring- matter  is  best  determined 
by  dye-trial ;  in  fact  this  is  the  only  trustworthy  method,  and  the 
numerous  processes  which  have  been  proposed  to  determine 
dyestuffs  voluinetrically  are  untrustworthy,  as  they  are  readily 
influenced  by  the  nature  of  the  impurities  present. 

Exceptions  may  be  made  in  dealing  with  a  few  dyestuffs  which 
come  into  commerce  in  a  pure  state. 

For  instance,  alizarin  is  tested  by  a  dye-trial,  and  then  examined 
after  washing  carefully  for  the  amount  of  solid  matter  and  ash 
which  it  contains. 

The  testing  of  colouring-matters  by  means  of  dye-trials  is  simply 


16  INTRODUCTION. 

colorimetric  comparison  of  a  dyestuff  with  a  standard  of  known 
quality.  If  equal  quantities  of  two  samples  of  a  dye  are  dyed 
upon  equal  weights  of  wool  or  silk,  a  difference  of  two  to  five  per 
cent,  may  be  distinguished  from  the  difference  in  shade  observed 
in  the  two  patterns. 

By  a  second  dyeing  it  is  easy  to  determine  the  difference  between 
the  quantities  of  the  two  dyestuffs  required  to  produce  the  same 
shade,  and  a  simple  calculation  then  gives  the  value  of  the  product 
tested,  compared  with  the  standard.  At  the  same  time  an  idea  is 
obtained  of  the  relative  purity  of  the  shade  of  the  dyestuffs  and 
of  the  nature  of  the  impurities  which  may  be  present. 

In  printing,  both  basic  dyestnffs  and  acid  ones  capable  of  forming 
lakes  with  metallic  oxides  are  employed. 

The  principle  of  the  fixation  of  basic  dyestuffs  in  printing 
depends  on  the  insolubility  of  the  tannin  compounds. 

The  tannates  of  all  colour-bases  are  insoluble  in  water,  but 
mostly  dissolve  in  dilute  acetic  acid.  The  dyestuff  is  printed 
along  with  tannin  and  dilute  acetic  acid.  The  acetic-acid  solution 
of  the  tannin  lake  penetrates  the  fibre,  and  subsequent  steaming 
removes  acetic  acid,  leaving  an  insoluble  lake  on  the  fibre.  The 
shades  may  be  made  faster  to  soap  by  passing  through  tartar 
emetic. 

Acid  dyestuffs,  like  alizarin  &c.,  are  printed  in  the  free  state 
along  with  the  metallic  mordants  (aluminium,  iron,  or  chromium 
acetate)  ;  on  steaming,  acetic  acid  is  driven  off  and  the  metallic 
oxide  combines  with  the  colour-acid  to  a  firmly  adhering  lake. 

Only  a  few  natural  dyestuffs  (indigo,  alizarin,  and  purpurin) 
have  been  prepared  synthetically,  but  the  number  of  artificial 
dyestuffs  is  very  large.  Some  of  these,  especially  the  phthalems 
and  rosolic  acid,  seem  to  approach  the  natural  dyestuffs  in  con- 
stitution, but  the  greater  number  belong  to  special  classes,  which 
are  without  analogue  in  either  the  animal  or  the  vegetable  kingdom. 

Natural  dyestuffs,  with  few  exceptions  (indigo,  berberine), 
contain  only  carbon,  hydrogen,  and  oxygen ;  while  many  classes 
of  artificial  colouring-matters  contain  nitrogenous  groups,  often 
of  a  decided  basic  nature.  Some  others  again  contain  chlorine, 


INTRODUCTION.  17 

bromine,  iodine,  or  sulphur.  The  raw  materials  for  the  preparation 
of  these  bodies  are,  at  the  present  time,  almost  exclusively  products 
of  dry  distillation,  and  the  most  important  of  these  is  coal-tar, 
obtained  as  a  bye-product  in  the  manufacture  of  illuminating-gas. 
The  discovery  and  first  preparation  of  artificial  dyestuffs  is  there- 
fore closely  associated  with  the  earliest  studies  on  products  of  dry 
distillation  ;  and  the  development  of  the  gas  industry  has,  hand  in 
hand  with  a  series  of  scientific  researches  appertaining  there- 
to, brought  the  important  colour-manufacturing  industry  into 
existence. 

The  honour  of  preparing  the  first  colouring-matters  from 
products  of  dry  distillation  belongs  to  von  Reichenbach  (pittacal 
from  wood-tar,  1832),  and  to  Runge  (rosolic  acid  from  coal-tar, 
1834) [1]. 

For  a  long  time,  however,  the  discoveries  of  these  chemists 
remained  in  obscurity,  and  it  was  only  after  the  knowledge  of 
products  of  dry  distillation  had  been  considerably  advanced  by 
later  researches,,  that  the  production  of  coloured  derivatives  again 
attracted  the  interest  of  chemists. 

Hofmaun,  Zinin,  and  Fritsche  were  the  first  to  show  the 
relationship  between  benzene,  aniline,  phenol,  &c. ;  and  the  first 
explanation  of  the  constitution  of  these  products  formed  the 
foundation  of  the  colour-industry. 

The  first  dyestuff  prepared  and  applied  on  an  industrial  scale 
was  "mauve,"  introduced  by  Perkin  in  1856.  About  the  same 
period  the  formation  of  rosaniline  was  noticed  by  Nathanson, 
who  obtained  it  by  heating  aniline  with  ethylene  chloride  [2] . 

Two  years  later  Hofmann  [3]  announced  the  discovery  of  a  red 
product,  obtained  by  the  action  of  carbon  tetrachloride  on  aniline. 
Hofmann  and  Nathanson,  if  their  experiments  were  made  with 
pure  aniline,  must  have  already  had  pararosaniline  in  their 
hands. 

The  next  ten  years  were  almost  entirely  devoted  to  the  scientific 
study  and  technical  development  of  rosaniline  and  its  derivatives. 

The  first  patent  was  taken  out  by  Renard  freres  and  Franc,  of 
Lyons,  on  April  8th,  1859  [4],  for  the  preparation  of  a  red  dyestuff, 


18  INTRODUCTION. 

according  to  a  process  discovered  by  Verguin,  which  consisted  in 
the  action  of  stannic  chloride  on  aniline. 

Numerous  patents  followed  in  England  and  France,  depending 
on  the  action  of  other  oxidising  agents  than  stannic  chloride.  In 
some  of  these  patents,  however,  it  is  not  clear  whether  rosaniline 
or  some  other  dyestuff  such  as  mauve  is  really  produced.  Renard 
frcres  introduced  their  products,  still  very  impure,  under  the 
name  "  fuchsine." 

The  process  of  Gerber-Keller  with  nitrate  of  mercury  is  the 
only  one  of  any  value  (October,  1859)  [5]. 

In  the  following  year,  1860,  the  application  of  arsenic  acid  as 
oxidising  agent  was  patented  by  Medlock  and  by  Nicholson  almost 
simultaneously  in  England  [6].  A  few  months  later  the  same 
process  was  made  the  subject  of  a  French  patent  by  Girard  and 
DeLaire  [7]. 

In  1861  Laurent  and  Castelhaz  [8]  patented  the  action  of  nitro- 
benzene on  iron  and  hydrochloric  acid,  and  this  is  evidently  the 
first  opening  of  the  nitrobenzene  process.  In  the  same  year  the 
synthesis  of  rosolic  acid  was  effected  by  Kolbe  and  Schmitt  [9] . 

The  formation  of  aniline  blue  was  also  first  observed  in  1861 
by  Girard  and  De  Laire ;  and  in  the  following  year  the  process 
was  further  developed  by  Nicholson  [10],  by  Monnet  and  Dury 
[11],  who  used  acetic  acid  in  the  manufacture,  and  by  "Wanklyn 
[12],  who  applied  benzoic  acid. 

In  1862  the  composition  of  rosaniline,  and  its  formation 
from  aniline  and  toluidine,  was  further  explained  by  A.  W. 
Hofmann  [13]. 

Aldehyde  green  was  also  discovered  in  1862  [14]. 
In  1863  the  same  chemist  prepared  ethyl-  and  methyl-deriva- 
tives   of   rosaniline,  and   showed   aniline   blue  to  be    triphenyl- 
rosaniline  [13]. 

Aniline  black  was  first  prepared  in  1863  by  Lightfoot  [15]. 
The  first  azo-dyestuffs  were  introduced  between  1864  and  1866. 
Amidoazobenzene  [16]  appeared  first,  and  was  quickly  followed  by 
phenylene  brown  []  7] . 

Caro  and  Wanklyn  [18]  demonstrated  the  relationship  between 


INTRODUCTION.  19 

rosaniline  and  rosolic  acid  in  1866 ;  and  in  the  same  year  Keisser 
took  the  first  patent  for  iodine  green  [19]  . 

Diphenylamine  blue  was  prepared  by  Girard  and  De  Laire  in 
1867  [20]. 

In  the  same  year  methyl  violet,  which  had  already  been  noticed 
by  Lanth  in  1861,  was  manufactured  on  a  large  scale  by  Poirrier 
and  Chapat. 

The  composition  of  iodine  green  was  determined  by  Hof  mann  and 
Girard  in  1869  [21]  ;  and  Rosenstiehl  demonstrated  the  existence 
of  several  rosanilines  [22] . 

The  synthesis  of  alizarin  was  carried  out  by  Graebe  and  Lieber- 
mann  [23]  in  the  same  year,  this  being  of  very  great  importance, 
as  the  first  synthesis  capable  of  industrial  application  for  production 
of  a  dyestuff  occurring  in  nature. 

In  1872  Hofmann  and  Geyger  [24]  examined  induline  and  saffra- 
nine,  the  latter  a  dyestuff  which  had  appeared  in  commerce  a 
few  years  previously. 

In  1873  Hofmann  published  his  researches  on  methyl  violet 
and  methyl  green  [25] . 

In  1874  the  phthalei'ns  (eosine),  discovered  by  Bayer  and  Caro, 
were  introduced  into  commerce. 

In  1876  pararosaniline  was  discovered  by  E.  andO.  Fischer,  and 
the  relation  of  this  body  to  triphenylmethane  demonstrated  [26] . 

In  1877  Prud'homme  discovered  alizarin  blue;  its  industrial 
production  was  effected  by  Brunck  in  the  following  year. 

In  the  same  year  Caro  [27]  produced  methylene  blue,  basing 
his  process  on  the  sulphuretted  hydrogen  reaction  observed  by 
Lauth  in  1876  [28].  Almost  simultaneously  malachite  green 
was  discovered  by  E.  and  O.  Fischer  [29]  and  by  Doebner  [30]  ; 
and  O.  N.  Witt  and  Houssin  introduced  the  synthesis  of  azo-dyes 
on  a  manufacturing  scale,  which  proved  afterwards  to  be  of  such 
great  importance. 

In  1880  Bayer  took  out  the  first  patent  for  the  production  of 
artificial  indigo  [31]. 

In  1881  this  was  followed  by  indophenol  [32]  and  the  gallo- 
cyanine  of  Witt  and  Koechlin. 


20  INTRODUCTION. 

In  1883-84  Caro  and  Kern  [33]  effected  the  synthesis  of  tri- 
phenylmethane  dyestuffs  by  means  of  carbon  oxychloride,  and  this 
was  applied  to  the  production  of  auramine  and  Victoria  blue. 

The  constitution  of  numerous  dyestuffs  has  been  determined  by 
purely  scientific  researches,  and  these  have  been  of  great  service 
in  discovering  new  synthetical  methods,  many  of  which  are  applied 
on  a  large  scale. 

In  1886  an  important  development  took  place  in  the  azo  colour- 
industry.  This  was  based  on  an  observation  made  by  Griess  (pat. 
1884),  that  certain  azo-dyestu  ffs  derived  from  benzidine  were 
capable  of  dyeing  vegetable  fibres  without  mordant.  As  members 
of  this  class  of  dyestuffs,  which  are  very  numerous,  may  be 
mentioned  chrysamine,  congo  red,  benzo-purpurine,  &c. 

In  1888  Witt  explained  the  constitution  of  the  saffranines  by 
his  classic  researches  on  the  azines;  and  not  long  afterwards, 
Fischer  and  Hepp  proved  that  the  indulines  were  also  derivatives 
of  azines. 

The  rhodamines,  a  class  of  dyestuffs  allied  to  the  phthalei'ns, 
were  introduced  in  1888. 

The  present  requirements  of  the  colour-industry  as  raw  materials 
are  benzene  and  its  homologues  (toluene  and  xylene),  naphtha- 
lene, and  anthracene,  obtained  from  coal-tar.  The  coal-tar  of 
the  gas-works  is  first  worked  up  in  tar-distilleries,  the  above  bodies 
being  obtained  in  a  more  or  less  impure  state.  The  further  purifi- 
cation is  carried  on  in  some  colour-works ;  but  this  generally 
takes  place  in  intermediate  manufactories  where  the  crude  products 
are  purified  and  worked  up  into  a  higher  stage,  benzene  and  its 
homologues  being  made  into  aniline,  toluidine,  and  xylidine,  and 
naphthalene  into  naphthylamine.  The  crude  benzol  is  first  sub- 
mitted to  a  careful  fractional  distillation,  and  benzene,  toluene, 
and  xylene  are  separated  in  as  pure  a  state  as  possible.  The 
hydrocarbons  boiling  at  a  higher  temperature  find  their  principal 
application  for  solvent  purposes,  hence  they  are  principally  met 
with  under  the  designation  "  solvent  naphtha/'  One  purpose  for 
which  it  serves  is  the  purification  of  anthracene.  Benzene, 


INTRODUCTION.  21 

toluene,    and   xylene  are   converted  into  aniline,  toluidine,   and 
xylidine  by  nitration  and  subsequent  reduction. 

These  bases  are  at  present  prepared  by  aniline-works  in  a  state 
of  great  purity ;  for  instance  the  aniline  employed  in  the  manu- 
facture of  blue  ("  blue  oil  ")  is  required  to  be  chemically  pure. 

The  "  red  oil "  used  in  the  manufacture  of  rosaniline  is  a 
mixture  containing  aniline,  ortho-  and  para-toluidine  in  varying 
proportions. 

A  classification  of  the  organic  dyestuffs  from  a  chemical  stand- 
point is  in  many  respects  a  subject  of  great  difficulty.  Most 
text-books  have  adopted  a  division  in  which  the  dyestuffs  are 
classified  according  to  the  hydrocarbon  from  which  they  are 
derived ;  this,  however,  is  far  from  natural,  as  by  its  means  some 
groups  which  are  chemically  well  characterized,  such  as  the  azo- 
dyes,  are  divided ;  and,  on  the  other  hand,  dyestuffs  of  totally 
different  constitution  are  placed  together. 

In  the  following  classification  an  attempt  is  made  to  group 
the  colour  ing- matters  according  to  their  chemical  constitution, 
especial  regard  being  paid  to  their  colour-giving  groups.  In  many 
cases  this  is  rendered  difficult,  however,  by  the  somewhat  scanty 
knowledge  of  the  relations  existing  between  constitution  and  dye- 
stuff  character. 

The  final  class,  "  Dyestuffs  of  unknown  constitution,"  is  still 
a  very  numerous  one. 

This  group  comprises  most  natural  dyestuffs :  the  constitution 
of  some  of  these  (alizarin  and  indigo)  is  known,  and  admits  of 
systematic  classification  with  just  as  much  justice  as  the  purely 
artificial  dyestuffs;  and  it  would  be  reasonable  to  treat  of  the 
whole  in  a  single  chapter  of  natural  dyestuffs. 

It  must  not  be  conceived  that  the  constitution  of  all  the  colouring- 
matters  here  classified  is  completely  explained,  in  many  cases 
it  is  deduced  from  analogy  in  formation  to  that  of  bodies  of 
known  constitution ;  but  as  to  the  constitution  of  dyestuffs  which 
have  not  been  prepared  synthetically,  we  are  altogether  without 
knowledge. 


22  INTRODUCTION. 

The  organic  colouring-matters  may  be  grouped  as  follows 
^*  I.  Nitro- Compounds. 
II.  Azo-Compounds. 

III.  Oxyquinones  and  Quinoneoximes. 

IV.  Ketone-imides  and  Hydrazides. 
V.  Triphenylmethane  Derivatives. 

VI.  Quinone-imide  Dyestuffs. 
-VII.  Azine  Dyestuffs. 
VIII.  Aniline  Black. 

IX.  Iridulines  and  Nigrosines. 
X.  Quinoline  and  Acridine  Dyestuffs. 

XI.  Indigo  Dyestuffs. 
XII.  Euxanthic  Acid  and  Galloflavine. 
XIII.  Canarine. 
XIV.  Murexide. 

XV.  Dyestuffs  of  unknown  constitution. 


> 


CHEMISTEY 


OP   THE 


ORGANIC  DYESTUFFS, 


CHAPTER  I. 

NITRO-COMPOUNDS. 

THE  nitro-derivatives  of  amines  and  phenols  are  dyestuffs,  of  a 
more  or  less  pronounced  character.  The  phenol  derivatives  have 
the  greater  tinctorial  power,  as  the  nitro-group  is  a  chromophor 
which  confers  acid  properties,  and  therefore  possesses  the  power 
of  decreasing  the  basic  properties  of  the  amido-group.  Indeed, 
in  the  case  of  certain  bodies  of  only  feebly  basic  properties,  the 
introduction  of  several  nitro- groups  may  produce  an  acid  dyestuff, 
for  example,  diphenylamine  is  a -body  of  this  class. 

Acid  nitro-compounds  are  especially  strongly  coloured  in  the 
form  of  salts ;  paranitrophenol,  for  example,  is  a  colourless  body, 
yielding  yellow  salts.  On  the  other  hand,  basic  nitro-compounds 
form  colourless  salts  with  acids. 

The  compounds  produced  when  the  acid  properties  of  the 
hydroxyl  group  are  removed  by  introduction  of  an  alcohol  radical 
are  colourless,  for  instance,  nitroanisol  behaves  like  a  nitro- 
derivative  of  a  hydrocarbon. 

Those  nitro  phenols  which  contain  the  nitro-  group  and  the 
hydroxyl  group  in  the  ortho  position  to  each  other,  are  as  a  rule 
the  most  strongly  coloured. 

The  close  relationship  existing  between  the  nitrophenols  and 


24  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

the  nitrosophenols,  and  the  assumption  generally  accepted,  that 
the  latter  are  quinoneoximes,  render  it  probable  that  a  similar 
structure  may  be  ascribed  to  the  nitrophenols,  and  that  in  the 
latter  there  is  a  certain  connection  between  the  nitro  and  hydroxyl 
groups. 

The  number  of  coloured  nitro-compounds  is  very  large,  and  in 
the  present  place  it  is  impossible  to  consider  more  than  those  which 
possess  technical  interest.  They  are  all  acid  dyestuffs  ;  since  the 
introduction  of  the  azo-dyestuffs  their  application  has  become 
considerably  less. 

Trinitrophenol  (PICRIC  ACID)  [1,  2,  3]. 
C6H2(N03)3OH. 

Picric  acid  is  formed  by  the  action  of  nitric  acid  on  phenol, 
and  on  many  other  organic  bodies  (indigo,  xanthorrhoea  resin, 
aloes,  &c.)  .  On  a  large  scale  it  is  obtained  by  the  action  of  con- 
centrated nitric  acid  on  phenol-sulphonic  acid.  [2]  . 

In  a  pure  state  picric  acid  forms  light  yellow  leaflets,  M.P. 
122°*  5  C.  It  dissolves  somewhat  sparingly  in  water,  more  easily 
in  alcohol. 

It  forms  well  crystallized  salts  with  metallic  oxides  ;  the 
potassium  salt,  C6H2(lSTO2yOK,  is  difficultly  soluble.  Picric  acid 
dyes  wool  and  silk  from  an  acid  bath,  a  fine  greenish  shade  of 
yellow  being  produced.  Although  this  shade  is  not  fast,  it  finds 
considerable  application  in  silk-dyeing,  and  serves  principally  for 
production  of  compound  colours,  especially  for  modifying  green 
and  red  dyestuffs. 

Dinitrocresol. 
TT  CHOH 


The  sodium  salt  of  a  dinitrocresol  formerly  came  into  commerce 
under  the  name  "  Victoria  Yellow"  or  Saffron  substitute  [5]. 

It  was  probably  obtained  by  treating  crude  creosol  with  nitric 
acid,  partly  also  by  diazotising  crude  toluidine  and  boiling  the 
resulting  compounds  with  nitric  acid.  It  consists  chiefly  of  a 
mixture  of  dinitroparacresol  (CH3  :  OH  :  NO2  :  NO2  =  1  .4.3.5), 
M.P.  83°-5,  and  dinitro-orthocresol  (1.2.3.5),  M.P.  85°'8  [4]. 
It  is  now,  however,  almost  out  of  the  market. 


NITRO-COMPOUNDS.  25 

RTIUS  YELLOW). 


C10H5(N03)3OH. 

Dinitro-a-naphthol  was  formerly  obtained  by  boiling  a-diazo- 
naphthalene  [6]  with  dilute  nitric  acid  ;  at  the  present  time  it 
is  manufactured  by  the  action  of  nitric  acid  on  a-naphthol  sul- 
phonic  acid  (mono-  or  di-sulphonic  acid)  [7]  . 

Pure  dinitronaphthol  forms  needles,  which  are  sparingly  soluble 
in  water  and  difficultly  soluble  in  alcohol,  ether,  or  benzene.  It 
melts  at  138°,  and  forms  salts  which  are  moderately  soluble  in 
water. 

The  commercial  product  is  generally  the  sodium  salt,  though  the 
lime  salt  is  occasionally  met  with.  It  dyes  wool  and  silk  in  an 
acid  bath,  a  fine  golden-yellow  shade  being  obtained.  The  principal 
drawback  in  the  use  of  this  dyestuff  is  that  it  is  volatile  at  a  com- 
paratively low  temperature,  and  is  therefore  liable  to  mark  off. 

Another  application  of  dinitronaphthol  is  for  colouring  con- 
fectionery, as  it  does  not  possess  the  bitter  taste  peculiar  to  most 
nitro-  compounds. 

^Dinitronaphthol  Sulphonic  Acid  (NAPHTHOL  YELLOW  S.) 

C10H4(NO2)2OH  HSO3. 

By  the  action  of  nitric  acid  on  a-naphthol  mono-  and  di-sul- 
phonic acids  (obtained  by  direct  sulphonation),  the  sulpho-groups 
are  replaced  by  nitro-groups,  while  on  nitration  of  a-naphthol 
trisulphonic  acid,  one  sulpho-group  remains  intact  [8],  the  other 
two  being  replaced  by  nitro-groups.  The  compound  formed  is  a 
monosulphonic  acid  of  dinitronaphthol.  This  acid  forms  long 
yellow  needles,  which  are  easily  soluble  in  water  [9]  . 

The  commercial  product  consists  of  the  potassium  salt,  which  is 
sparingly  soluble.  On  wool  and  silk  it  dyes  the  same  shades  as 
Martius  yellow,  but  is  to  be  preferred  as  yielding  much  faster  dyes. 

It  may  be  distinguished  from  Martius  yellow  by  treating  its 
solution  with  acids  ;  Martius  yellow  is  immediately  precipi- 
tated, while  naphthol  yellow  S  gives  no  reaction. 


26  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


Brilliant  Yellow. 

This  dyestuff  is  prepared  by  the  nitration  of  the  a-naphthol 
disulphonic  acid  of  the  Schollkopf  Co.  It  is  an  isomer  of  naphtLol 
yellow  S,  but  little  is  known  of  its  dyeing  properties. 

Tetranitronaphthol  [10]. 

C10H3(N02)46H. 

Tetranitro-a-naphthol  is  obtained  from  tetranitrobromnaph- 
thalene  by  treating  with  an  alkali.  It  forms  yellow  needles  which 
melt  at  180°.  It  gives  fine  orange  shades  on  wool  and  silk,  but 
it  is  not  fast  to  light,  and  has  only  obtained  slight  appreciation 
under  the  designation  "  Sun  gold.1" 

Tetranitrodiphenol. 


This  colouring-matter  formerly  came  into  commerce  in  form 
of  its  ammonium  salt  as  "  Palatine  orange,"  and  was  used  in 
paper-dyeing.  It  is  formed  by  treating  benzidine  with  nitrous 
acid,  and  boiling  the  resulting  tetrazodiphenyl  with  nitric  acid. 

Hexanitrodiphenylamine  (AUEANTIA)  [11]. 
(N02)3C6H2NHC6H2(N02)3. 

Hexauitrodiphenylamine  is  produced  by  energetic  action  of 
nitric  acid  on  diphenylamine.  It  forms  yellow  prisms,  M.P.  238°, 
and  behaves  like  an  acid,  forming  stable  crystalline  salts  with  the 
alkalies.  It  dyes  an  orange  shade  on  silk  and  wool,  but  since  the 
introduction  of  the  azo-dyes  is  scarcely  ever  used. 

Salicyl  Yellow  (NITROBROMSALICYLIC  ACID)  [13]. 

The  iiitro-compounds  which  are  formed  by  treating  monobrom- 
salicylic  acid  with  nitric  acid  have  been  tried  experimentally  in 
dyeing.  They  are  very  fugitive  to  light,  and  this,  together  with 
their  high  price,  renders  them  unsuitable  for  technical  application. 


NITRO-COMPOUNDS.  27 

Mononitrobromsalicylic  acid  dyes  a  very  pure  yellow  on  wool  and 
silk  from  an  acid  bath,  the  dinitro- compound  yields  a  more  orange 
shade. 

Isopurpuric  Acid. 
C8H5N506. 

The  potassium  salt  of  this  acid,  which  is  also  known  as  picro- 
cyaminic  acid,  is  obtained  by  treating  picric  acid  with  solution  of 
potassium  cyanide.  The  ammonium  salt  obtained  from  the 
potassium  salt  by  double  decomposition  with  ammonium  chloride 
was  formerly  used  in  dyeing  under  the  name  "  Grenat  soluble." 
It  produces  reddish-brown  shades  on  wool  and  silk,  but  has  now 
entirely  disappeared. 

Another  colouring-matter  which  formerly  occurred  in  commerce 
is  picramic  acid,  C6H2(NO2)3NH2OH,  obtained  from  picric  acid 
by  partial  reduction. 


28  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


CHAPTER  II. 

AZO-COMPOUNDS. 

THE  Azo-dyestuffs  form  a  well- characterized  group  of  compounds 
containing  the  azo-chain  — N=N —  as  chromophor. 

This  divalent  group  is  always  linked  with  two  benzene  rings  or 
other  aromatic  hydrocarbon,  and  thus  differs  from  the  diazo-group, 
which  is  similarly  constituted  in  other  respects.  The  introduction 
of  the  azo-group  into  hydrocarbons  or  bodies^cting  similarly 
(anisol,  phenetol)  gives  rise  to  the  formaij^Bf  coloured  com- 
pounds, which,  however,  are  not  dyestuffs.^^ie  affinity  for  fibres 
is  only  acquired  when  groups  are  introduced  which  confer  acid  or 
basic  properties  to  the  azo-compounds. 

Azobenzene,  though  intensely  coloured,  is  not  a  dyestuff. 
Azobenzene-sulphonic  acid  possesses  tinctoria^P^opj^p^ilthough 
only  to  a  slight  extent ;  but  if  auxochrorrac  groupl^uch  as  the 
amido  or  hydroxyl  groups,  are  present,  the  dyeing  power  is  con- 
siderably increased,  and  at  the.  same  time  the  shade  is  considerably 
modified.  It  is  probable  that  in  this  class  of  compounds  there 
exists  a  certain  linkage  between  the  auxochromic  and  the  chromo- 
genic  groups,  this  linkage  being  easily  dissolved  under  certain 
circumstances. 

Liebermann  deduced  the  following  formula  for  /3-naphthol-azo- 
benzene  [1], 

C6H5-N-N 

I  /U10M6, 

from  the  fact  that  this  body  does  not  act  as  a  phenol.  In  a  similar 
manner  Zincke  ascribes  one  of  the  following  formulae  to  the  com- 
pound produced  by  the  interaction  of  diazobenzene  and  /3-naph- 
thylamine  [2]  : — 


AZO-COMPOUXDS.  29 

C6H5-NH-N 

pC10Ha       or     C6H5- 

H 

It  cannot  be  denied  that  many  reactions  of  oxy-  and  amidoazo- 
compounds,  especially  those  of  the  ortho  series,  are  easily  explained 
on  the  assumption  that  these  formulae  are  correct;  but,  on  the 
other  hand,  amidoazo-compounds  are  capable  of  reacting  as  true 
amines. 

The  above  formulae  show  a  certain  analogy  to  the  quinones, 
especially  marked,  if  written  slightly  differently, 

C6H5-NH-N=C10H6  =  O    and     C6H5-NH-N  =  C10H6  =  NH. 

An  important  support  for  this  theory  is  the  circumstance  that 
the  bodies  formed  by  the  action  of  aromatic  hydrazines  on 
quinones  are  identical  with  those  obtained  from  phenols  and 
diazo-compounds.  Phenylhydrazine,  for  example,  reacts  with 
a-naphthoquinone,  producing  the  same  compound  which  is  formed 
by  combination  of  a-naphthol  with  diazobenzene  [3j.  The  first 
method  of  formation  renders  the  formula 

C6H5-NH-N=C10H6  =  0 

probable,  while   the   latter  affords  just  as  good  reason  for  the 
formula 

C6H5-N=N-C10H6-OH. 

The  compounds  from  hydrazines  and  ketones  or  quinones 
(hydrazides)  are  so  closely  related  to  the  azo-series,  that  one  is 
almost  compelled  to  place  them  under  the  same  classification. 

The  property  of  forming  combinations  with  sodium  bisulphite  is 
common  alike  to  azo-dyes,  .ketones,  and  quinones  [4] .  A  differ- 
ence in  the  constitution  of  ortho-  and  para-derivatives  cannot  well 
be  accepted,  as  the  same  reactions  may  be  obtained  with  each, 
though  with  varying  degrees  of  ease. 

As  has  already  been  stated,  the  azo- compounds  react  like  amido- 
or  hydroxyl  compounds  in  certain  cases ;  for  example,  all  amido- 
azo-compounds yield  diazo-compounds.     It  is  possible  that  two  t 
forms  exist  in  such  cases,  and  that  these  react  in  one  way  or 
another  according  to  circumstances. 


30  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

The  older  constitutional  formulae  have  been  used  in  the  following 
pages,  this  being  the  general  method,  and  as  there  is  just  as  much 
evidence  in  favour  of  the  old  formulae  as  there  is  for  the  new. 
The  simplest  azo-compounds,  like  dyestuffs  of  simple  constitution, 
have  in  general  a  yellow  colour.  By  increasing  the  number  of 
auxochromic  groups,  or  by  building-up  of  carbon  atoms  in  the 
molecule,  the  shade  becomes  deeper.  In  many  cases  it  goes 
through  red  to  violet,  in  others  it  becomes  brown.  Blue  dyestuffs 
of  this  class  have  only  been  obtained  by  introduction  of  several 
azo-groups  in  the  molecule  (dis-  or  tetrazo-dyestuffs). 

Azo-dyestuffs  of  a  green  colour  have  not  yet  been  obtained, 
although  many  form  green  compounds  with  acids. 

The  so-called  uazo-green,"  although  containing  an  azo-group, 
owes  its  colour  to  the  rest  of  triphenylmethane  present. 

Dyestuffs  which  contain  benzene  and  no  higher  hydrocarbon  are 
mostly  yellow,  orange-yellow,  or  brown.  By  the  introduction  of  a 
naphthalene  group,  red  colouring-matters  are  formed,  and  blue  and 
violet  dyestuffs  are  obtained  if  the  naphthalene  ring  occurs  several 
times. 

The  introduction  of  a  radical  of  totally  indifferent  properties  (as 
the  methoxyl  group,  — O  CH3)  may  produce  a  great  alteration  in 
the  colour  of  the  compound  operated  upon. 

The  relative  positions  of  the  chromophor  groups  have  also  a 
decided  influence  in  this  direction.  The  compound 

(HS03)2  NC 

0/^10  tL4  —  JN  2  —  ^6  tt4  —  -N  2<-  lo 

is  blue  if  the  azo-groups  are  in  the  para-position  in  the  benzene 
ring,  and  red  if  in  the  meta-position. 

"1  The  general  rule  that  the  depth  of  colour  of  a  compound 
increases  with  the  number  of  atoms  constituting  the  molecule,  does 
not  apply  in  all  cases ;  for  example,  the  above  dyestuff  is  redder,  if 
the  connecting  benzene  ring  is  replaced  by  a  higher  hydrocarbon. 
Nearly  all  azo-dyestuffs  give  characteristic  colour-reactions  on 
dissolving  in  strong  sulphuric  acid,  and  it  is  probable  that  in  such 
cases  the  basic  properties  of  the  azo-group  become  apparent  by  the 
action  of  the  strong  acid.  It  is  worthy  of  notice  that  most  sub- 
stituted azo-dyes  give  the  same  reaction  with  sulphuric  acid  as  the 


AZO-COMPOUNDS.  31 

azo-hydrocarbon  from  which  they  are  derived.  Azobenzene  dis- 
solves in  sulphuric  acid  with  a  yellowish-brown  colour;  and  the  same 
colour  is  obtained  with  its  oxy-  and  amido-derivatives,  although 
the  latter  are  coloured  red  by  dilute  acid,  a-azo-naphthalene,  and 
its  oxy-  and  amido-derivatives,  give  a  blue  coloration  with  concen- 
trated sulphuric  acid.  In  mixed  azo-compounds  the  presence  of  a 
sulpho-group  may  produce  interesting  changes  according  to  its 
position.  /3-naphthol-azobenzene,  for  example, 

C6H6-NS-C10H6OH, 

dissolves  in  sulphuric  acid  with  a  red-violet  colour,,  probably  the 
same  which  belongs  to  the  mother  substance, 

C6H5 — N2 — C10H7. 

The  same  colour  is  obtained  if  a  sulpho-group  occurs  in  the  benzene 
ring ;  while,  on  the  other  hand,  if  this  group  is  in  the  naphthol,  the 
compound  dissolves  with  a  yellow  colour,  the  same  as  azobenzene. 

These  phenomena  may  be  explained  on  the  assumption  that  the 
sulpho-group  exerts  a  salt-forming  action  with  one  nitrogen  atom 
of  the  azo-chain ;  and  that  in  one  case  with  the  above  compound, 
the  nitrogen  atom  attached  to  the  benzene  ring  is  influenced,  in 
the  other  that  combined  with  the  naphthalene. 

These  colour- reactions  become  more  complicated  if  several  azo- 
groups  are  present  in  the  molecule. 

Substituted  azo-compounds  are  generally  prepared  by  the  action 
of  diazo-compounds  on  phenols  and  amines.  With  the  latter 
bodies  the  intermediate  formation  of  diazo-amido  compounds  is 
often  observed. 

Experience  has  proved  that  the  azo-group  enters  in  the  para- 
position  to  the  amido-  or  hydroxyl-group  if  this  is  free;  if  this 
point  is  already  substituted,  the  linkage  takes  place  in  the  ortho- 
position.  Condensations  in  the  meta-position  have  till  now  not 
been  observed. 

Some  azo-compounds  may  be  converted  into  easily  oxidisable 
hydrazo-compounds  by  cautious  reduction,  while  all  are  decom- 
posed by  the  action  of  energetic  reducing  agents.  In  this  case  the 
linkage  between  the  nitrogen  atoms  is  dissolved,  each  atom  being 
converted  into  an  amido-group  by  addition  of  hydrogen.  Azo- 
benzene yields  on  reduction  two  molecules  of  aniline ;  amidoazo- 


32  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

benzene  gives  one  molecule  of  aniline  and  one  molecule  of  para- 
phenylenediamine, 


This  splitting  up  forms  in  many  cases  a  means  for  recognition 
of  azo-compounds  and  for  determining  their  constitution.  By  far 
the  greater  number  of  azo-dyestuffs  used  technically  are  sulphonic 
acids,  while  the  number  of  basic  azo-dyes  is  limited.  Amidoazo- 
compounds  of  weak  basic  properties  are  not  easily  fixed  in  dyeing  ; 
they  yield,  however,  useful  basic  dyestuffs  if  a  second  amido-group  is 
introduced  into  the  ring,  which  already  contains  the  auxochrome 
group.  Probably  this  second  group  does  not  act  as  an  auxochrome  ; 
it  has  no  connection  with  the  azo-chain,  and  its  function  is  appa- 
rently to  supply  the  necessary  attraction  for  the  fibre.  If  both 
amido-groups  are  in  different  rings,  the  resulting  compound  acts 
as  a  simple  amidoazo-compound. 

Chrysoidine, 

C6H5-NS-C6H3(NH2)2) 

for  example,  is  a  strong  basic  dyestuff,  while  in  an  isomer  parazo- 
aniline, 

NH2C6H4-N2-C6H4NH2, 

this  property  is  absent.  Probably  in  the  latter  case  both  amido- 
groups  are  influenced  to  a  certain  extent  by  the  azo-chain,  while 
with  chrysoi'dine  this  is  only  the  case  with  one  group. 

The  amido-groups  acting  as  auxochromic  groups  are  therefore 
probably  connected  with  the  azo-group,  and  when  combined  with 
acids  to  form  salts  show  a  striking  alteration  in  colour,  while  the 
amido-groups,  which  play  merely  a  basic  part,  do  not  undergo 
this  change. 

Chrysoidine,  a  case  in  point,  forms  stable  salts  with  one  molecule 
of  acid,  and  their  colour  is  little  different  to  that  of  the  base,  while 
with  an  excess  of  acid  a  red  di-acid  salt  is  formed,  which  loses  the 
second  molecule  of  acid  on  treatment  with  water.  On  the  other 
hand,  amidoazobenzene  forms  red  salts  which  are  decomposed  by 
water. 

Parazoaniline,  which  in  all  probability  contains  two  auxochromic 
amido-groups,  shows  different  colours  according  as  one  or  both  of 
these  groups  are  saturated.  With  acids  it  gives  at  first  a  green 
colour  ;  in  presence  of  excess,  however,  a  red  colour. 


AZO-COMPOUNDS.  33 

Certain  facts  render  it  doubtful  whether  the  auxochromic  amido- 
groups  enter  into  combination  with  the  acid  radical  in  the  forma- 
tion of  salts,  and  it  is  possible  that  the  azo-group  enters  into 
combination.  Amidoazobenzene,  a  weak  base,  retains  its  basic 
properties  after  acetylation,  and  forms  red  salts  as  before ;  while 
the  simple  amines  such  as  aniline,  which  possess  much  stronger 
basic  properties,  yield  on  acetylation  almost  completely  indifferent 
compounds.  At  any  rate  this  fact  strongly  supports  the  assumption 
that  there  is  a  certain  linkage  between  the  azo-  and  amido-groups. 

The  sulphoriic  acids  of  the  amidoazo-compounds  are  interesting 
in  this  respect.  Apparently  they  are  incapable  of  existing  in  the 
free  state,  at  least  from  their  colour  it  appears  that  the  formation 
of  a  salt  takes  place  between  the  sulpho-group  and  the  basic 
group. 

Amidoazobenzene  in  the  free  state  is  yellow,  while  its  sul- 
phonic  acids  have  the  red  colour  of  the  amidoazobenzene  salts. 
If,  however,  the  sulpho-group  is  saturated  by  an  alkali,  the  salt 
produced  has  again  the  colour  of  free  amidoazobenzene. 

These  amido-sulphonic  acids  behave  like  acid  dyestuffs,  but  in 
dyeing  the  fibre  always  takes  the  colour  of  their  alkali  salts  or  of 
the  free  amidoazo-base. 

The  conclusions  naturally  drawn  from  this  are  that  the  sulpho- 
group  effects  the  combination  with  the  fibre,  and  that  the  acid 
properties  of  the  former  are  saturated  by  the  latter. 

This  property  is  still  more  striking  with  the  sulphonic  acid  of 
phenyl  amidoazobenzene  (Tropaolin  OO) ;  this  body  exhibits  a 
colour- change  from  orange  to  violet. 

The  azo-compounds,  though  long  known,  have  attained  most  of 
their  importance  in  the  last  ten  years,  especially  the  scarlet-red 
shades,  which  have  almost  entirely  replaced  cochineal.  The  first 
azo-dyestuff  used  largely  was  triamidoazobenzene  (phenylene 
brown)  discovered  by  Caro  and  Griess  in  1867. 

For  ten  years  after  this  no  particular  progress  was  made  in  this 
field,  and  the  first  synthetical  production  of  azo-compounds 
appears  with  the  discovery  of  chrysoidine  by  Witt  and  Caro. 

ChrysoVdine  was  rapidly  followed  by  the  introduction  of  the 
acid  dyestuffs,    discovered   almost   simultaneously   by   Witt  and 
Roussin,  and  which,  since   the   introduction  of  naphthols,  have 
attained  great  importance. 
^  The  manufacture  of  azo-dyes  is  in  general  very  simple.     If  a 

D 


34  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

diazo-compound  has  to  be  combined  with  a  phenol,,  the  former  is 
prepared  by  dissolving  the  amine  or  its  sulphonic  acid  in  water,  or 
suspending  them  in  as  finely  divided  a  state  as  possible,  and  adding 
to  the  liquid  the  calculated  quantities  of  hydrochloric  acid  and 
sodium  nitrite. 

After  diazotisation  is  completed  the  liquid  is  allowed  to  run 
into  an  alkaline  solution  of  the  phenol  or  its  sulphonic  acid,  care 
being  taken  that  the  mixture  remains  alkaline.  After  some  time 
the  dyestuff  is  salted  out,  and  is  generally  filtered  through  a 
filter-press.  The  combination  of  diazo-compounds  with  amines 
is  somewhat  more  complicated.  Some  of  these,  for  instance 
metaphenylenediamine,  combine  with  diazo-compounds  in  neutral 
aqueous  solutions;  while  others,  like  diphenylamine,  are  dissolved 
in  alcohol,  and  a  concentrated  solution  of  the  diazo-compound 
gradually  added.  In  the  manufacture  of  amidoazobenzene  and 
all  compounds  in  which  an  intermediate  formation  of  a  diazo- 
amido-compound  takes  place,  a  large  excess  of  the  amine  has  to  be 
employed,  to  hold  the  diazoamido-compound  formed  in  solution. 

Sulphonic  acids  are  generally  obtained  by  combination  of  diazo- 
sulphonic  acids  with  phenols  or  diazo-bases  with  phenolsulphonic 
acids,  in  a  few  cases  also  by  heating  the  azo-compound  with 
fuming  sulphuric  acid. 

The  principal  application  of  azo-dyestuffs  is  in  wool-dyeing, 
and  all  acid  azo-dyes  may  be  directly  dyed  on  animal  fibres  from 
an  acid  bath. 

On  cotton  they  are  generally  incapable  of  complete  fixation,  as 
most  of  them  form  no  real  colour-lakes.  Exceptions  to  this  rule 
are  certain  tetrazo-compounds  which  dye  cotton  directly  in  the 
form  of  alkali  salts  of  their  sulphonic  acids. 

Basic  azo-dyes  (chrysoi'dine,  Bis  mark  brown)  are  dyed  like  all 
colour-bases  on  vegetable  fibres  prepared  with  tannic  acid.  Their 
principal  application  is  in  cotton-dyeing. 

A  uniform  method  of  nomenclature  for  all  azo-compounds  is 
much  to  be  desired,  but  the  strict  application  of  such  a  principle, 
further  than  formation  into  groups,  would  lead  to  the  necessity  for 
very  long,  and  often  unwieldy  names,  without  insuring  certainty 
in  regard  to  position. 

For  this  reason  such  a  method  has  been  avoided,  and  the  bodies 
are  in  general  described  under  the  names  given  them  by  their 
discoverers. 


AMIDOAZO-COMPOUNDS.  35 


I.  AMIDOAZO-COMPOUNDS. 

Amidoazobenzene  [5,  6]. 

(1)  (4) 

C6H5-N=N-C6H4NH2. 

Amidoazobenzene  is  formed  by  the  molecular  transformation 
which  diazoamidobenzene  undergoes  when  -brought  in  contact 
with  aniline  hydrochloride,  best  in  aniline  solution.  It  is  there- 
fore the  final  product  of  the  reaction  which  occurs  when  a  salt  of 
diazobenzene  is  treated  with  an  excess  of  aniline,  at  a  medium 
temperature. 

Its  manufacture  on  a  large  scale  depends  on  this  principle : 
Aniline  is  treated  with  such  quantities  of  hydrochloric  acid  and 
sodium  nitrite,  that  about  a  third  is  converted  into  diazoamido- 
benzene, and  that  the  latter  remains  dissolved  in  the  excess  of 
aniline.  Further,  the  amount  of  hydrochloric  acid  is  so  calculated, 
that  after  decomposition  of  the  nitrite  some  aniline  hydrochloride 
remains  in  the  mixture.  The  conversion  of  the  diazoamido- 
benzene is  aided  by  warming  gently,  and,  when  complete,  the 
excess  of  aniline  is  saturated  with  dilute  hydrochloric  acid,  and 
filtered  from  the  sparingly  soluble  amidoazobenzene  hydro- 
chloride. 

Free  amidoazobenzene  forms  yellow  needles  melting  at  127°' 5, 
which  may  partly  be  sublimed  without  decomposition. 
*  Its  salts  with  acids  are  red  and  very  unstable.  They  crystallise 
well,  and  possess  a  bluish  reflex.  They  are  decomposed  by  water, 
and  are  difficultly  soluble  in  dilute  acids,  a  red  solution  being 
produced.  With  concentrated  sulphuric  acid,  amidoazobenzene 
gives  a  yellowish-brown  solution.  It  is  easily  split  up  on  reduc- 
tion, aniline  and  paraphenylenediamine  being  formed. 

By  cautious  treatment  with  zinc  powder  in  alkaline  solution  it 
is  converted  into  amidohydrazobenzene,  a  colourless  compound 
which  oxidises  rapidly  on  exposure  to  the  air. 
4  Amidoazobenzene  itself  is  useless  as  a  dyestufd,  but  is  important 
as  a  starting-point  for  the  manufacture  of  various  dyestuffs. 


36  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

An  isomer  of  amidoazobenzene,  which  contains  the  amido-  and 
azo-groups  in  the  ortho  position,  has  recently  been  obtained  by 
Janovsky  [7]. 


Amidoazolenzenemonosulplionic  Acid  [8,  9]. 

(1)  (4)        (1)  (4) 

HSO3C6H4-N=N-C6H4NH3. 

This  acid  is  obtained  with  the  disulphonic  acid  by  treating 
amidoazobenzene  with  fuming  snlphnric  acid.  It  is  formed  in 
small  quantities  by  the  action  of  paradiazobenzenesulphonic 
acid  on  aniline  hydrochloride.  It  may  also  be  obtained  by 
cautious  reduction  of  nitroazobenzenesulphonic  acid. 

As  obtained  by  decomposition  of  its  salts  with  hydrochloric 
acid,  it  forms  a  gelatinous  flesh-coloured  precipitate,  which  after 
some  time  changes  to  needles.  Its  salts  throughout  are  sparingly 
soluble  in  cold  water,  but  dissolve  easily  in  hot  water.  The 
sodium  salt  forms  golden-yellow  leaflets. 


Amidoazobenzenedisulphonic  Acid  [8,  9]. 

(1)  (4)        (1)  (4) 

HS03 .  C6H4N=N-C6H3NH3S03H. 

This  acid  is  produced  by  the  energetic  action  of  fuming  sulphuric 
acid  on  amidoazobenzene.  It  forms  shimmering  violet  crystals 
resembling  chromic  chloride,  which  on  drying  disintegrate. 

The  acid  is  easily  soluble  in  water,  but  separates  on  addition  of 
a  mineral  acid.  Its  salts  are  yellow,  very  easily  soluble,  and 
difficult  to  crystallise. 

The  sulpho-groups  are  present  in  both  rings,  and  on  reduction 
the  body  yields  sulphanilic  and  paraphenylenediaminesulphonic 
acids. 

Both  these  sulphonic  acids  of  amidoazobenzene,  and  especially 
the  disulphonic  acid,  are  valuable  yellow  dyestuffs,  and  the  sodium 
salt  of  the  latter  comes  into  commerce  as  Acid  Yellow  or  Fast 
Yellow.  A  further  application  of  these  acids  is  in  the  preparation 
of  tetrazo-dyestuiFs,  for  example  Biebrich-  and  Crocein-scarlets. 


AMIDOAZO-COMPOUNDS.  37 


Acetylamidoazolenzene  [71], 
C6H5— N=N— C6H4Np  H  n, 

v>/2-Ll-3v-' 

forms  yellow  leaflets  melting  at    141°.      It  dissolves   in  hydro- 
chloric acid  with  a  red  colour,  and  is  only  saponified  on  boiling. 


Dimethylamidoazobenzene  [10]. 

(1)  (4) 

CH3 
Dimetlrylamidoazolenzenesulphonic  Acid  [11]. 

(1)  (4)        (1)  (4) 

HS03-  C6H4-^  =N-C6H4-N(CH3)2. 

Dimethylamidoazobenzene  is  obtained  by  action  of  dimethyl- 
aniline  on  hydrochloride  of  diazobenzene,  and  if  the  latter  be 
replaced  by  diazobenzeDesulphonic  acid,  the  above  monosulphonic 
acid  is  formed. 

The  base  forms  golden-yellow  leaflets  melting  at  115°.  Its 
hydrochloride,  C14,H13N3,HC1,  forms  violet  needles  sparingly 
soluble  in  water.  The  basic  character  of  amidoazobenzene  seems 
to  be  increased  by  introduction  of  alcohol  radicals  into  the  amido- 
group,  as  the  salts  of  dimethylamidoazobenzene  are  far  more 
stable  than  those  of  amidoazobenzene.  A  dilute  solution  of  the 
base  becomes  reddened  by  a  trace  of  acid,  and  on  this  fact 
depends  its  application  as  an  indicator  in  alkalimetry.  Acetic  acid 
and  amidosulphonic  acids  are  without  action  on  the  compound. 
Dimethylamidoazobenzene  is  sometimes  used  for  colouring  butter 
and  candles. 

The  monosulphonic  acid  forms  brilliant  violet  needles,  which 
are  sparingly  soluble.  Its  salts  are  yellow,  and  mostly  well 
crystallised. 

The  calcium  salt  is  obtained  as  a  lustrous  precipitate  by  adding 
calcium  chloride  to  a  solution  of  the  sodium  salt. 

The  sodium  salt  of  this  sulphonic  acid  has  been   used  as   a 


38  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

dyestuff  under  the  names  Tropaolin  II,  Orange  III,  and  Heli- 
anthine.  It  gives  fine  orange  shades  on  wool  and  silk,  but  owing 
to  its  sensitiveness  towards  acids  has  not  met  with  great  success. 


Phenylamidoazolenzene  [12], 
C6H6-N=N-C6H4NHC6H5, 

is  formed  by  the  action  of  diazobenzene  chloride  on  diphenyl- 
amine.  It  crystallises  in  golden-yellow  prisms  or  leaflets. 
M.P.  82°. 

It  is  soluble  in  alcohol,  ether,  benzene,  and  ligroine,  insoluble 
in 'water.  Acids  colour  the  alcoholic  solution  violet,  the  salts 
being  precipitated  as  grey  crystals.  It  dissolves  in  concentrated 
sulphuric  acid  with  a  green  colour,  changing  through  blue  to 
violet  on  dilution  with  water.  By  action  of  amyl  nitrite  a  nitros- 
amine,  M.P.  119°'5,  is  obtained.  On  reduction  it  yields  aniline 
and  paramidodiphenylamine. 


Phenylamidoazolenzenesulphonic  Acid  [12]. 

(1)  (4) 


(TROPAOLIN  OO,  OEANGE  IV.) 

Is  obtained  by  action  of  p-diazobenzenesulphonic  acid  on  an 
acid,  alcoholic,  dipheriylamine  solution.  The  free  acid  forms 
needles  resembling  graphite,  which  dissolve  sparingly  in  water 
with  a  red-  violet  colour.  The  salts  are  well  crystallised,  and,  with 
the  exception  of  the  insoluble  calcium  and  barium  salts,  dissolve 
easily  in  hot  water,  less  easily  in  cold  water.  Concentrated 
sulphuric  acid  dissolves  the  compound,  forming  a  violet  solution. 
The  sodium  salt  has  a  large  application,  and  comes  into  commerce 
under  the  above  designations.  It  dyes  wool  and  silk  a  beautiful 
orange. 

An  isomeric  compound  prepared  from  metamidobenzene- 
sulphonic  acid  is  known  as  Metanil  Yellow  and  dyes  somewhat 
yellower  shades. 


AMIDOAZO-COMPOUNDS.  39 

Yellow  dyestuffs  are  also  obtained  by  action  of  diazotoluene- 
sulphonic  acids  on  diphenylamine. 

Nearly  all  phenylamidoazo-compounds  yield  nitro-derivatives 
when  their  nitrosamines  are  carefully  treated  with  nitric  acid. 
The  nitro-group  enters  into  the  diphenylamine,  and  certain 
bodies  obtained  in  this  manner  are  used  under  the  names  Azo- 
flavine,  Citronine,  and  Indian  Yellow.  They  are  distinguished 
from  the  original  dyestufFs  by  their  yellower  shade. 

Experimental  trials  have  also  been  made  with  higher  sulphonic 
acids  of  phenylamidoazobenzene. 


Amidoazotoluenebenzene  [1 3]. 

(1)  (4)         (1)  (4) 

C6H4CH3  -  N  =  NC6H4NH2. 

From  paradiazotoluene   and  aniline.      Forms  long  yellowish- 
brown  needles  melting  at  147°. 


Amidoazotoluenes. 

(1)  (2)         (1)  (3)        (4) 

A.  C6H4CH3-N=N-C6H3CH3KH3.     [13] 

Is  obtained  from  orthotoluidine  in  a  similar  manner  to  amido- 
azobenzene  from  aniline.     M.P.  100°. 

(1)  (-4)       (1)  (»)          (4) 

B.  C6H4CH3-N  =  N-C6H3CH3NH2.     [13] 

From  paradiazotoluene  and  orthotoluidine.     M.P.  127-128°. 

(1)  (3)        (1)  (2)         (4) 

C.  C6H4CH3-N  =  N-C6H3CH3NH3.     [13] 
From  metatoluidine.     M.P.  80°. 

(1)  (4)        d)  (2)        (4) 

D.  C6H4CH3-N=N-C6H3CH3NH2.       [13]  , 

By  the  action  of  paradiazoamidotoluene  on  metatoluidine.    M.P. 
127°. 

(1)  (4)        (1)  (4)        (2) 

E.  C6H4CH3-N=N-C6H3CH3NH2.     [14] 

By  the  interaction  of  paradiazoamidotoluene  and  paratoluidine. 
M.P. 


40  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

These  amidoazotoluenes,  when  treated  with  fuming  sulphuric 
acid,  yield  sulphonic  acids,  some  of  which  are  used  as  yellow 
dyes  tuffs. 

The  first  four  amidoazotoluenes,  A,  B,  C,  D,  contain  the  amido- 
group  in  the  para  position  to  the  azo-group.  They  are  all  reddened 
by  acids,  and  yield  paradiamidotoluene  on  reduction. 

The  last  compound,  E,  contains  the  groups  in  the  ortho  position  ; 
it  is  coloured  green  by  acids,  and  yields  orthodiamidotoluene  on 
reduction. 

Amidoazoxylenes, 

Seven  isorneric  amidoazoxylenes  are  known,  but  for  a  description 
reference  must  be  made  to  the  literature  of  the  subject  [15, 16]. 

Generally  speaking,  their  properties  are  similar  to  those  of 
amidoazobenzene  and  the  amidoazotoluenes. 


Diamidoazolenzenes  [12,  13], 

A.  Cliryso'idine  [17,  18]. 
(i) 


Chrysoidine  is  prepared  by  mixing  equivalent  quantities  of 
solutions  of  diazobenzene  chloride  and  metaphenylenediamine. 
The  base  crystallises  from  hot  water  in  yellow  needles,  M.P. 
117°'5.  It  dissolves  sparingly  in  water,  easily  in  alcohol,  ether, 
and  benzene  [18]. 

It  forms  two  series  of  salts  with  acids  [18]  ;  the  monoacid  salts 
are  stable  and  yellow  in  solution,  the  diacid  salts  are  red  and  are 
decomposed  by  water. 

C12H13N4,HC1  is  obtained  in  two  forms  according  to  whether 
it  has  been  crystallised  rapidly  or  slowly.  In  the  first  case  it 
forms  long  red  felted  needles,  and  in  the  latter  anthracite  black 
aggregates  of  octahedrons  possessing  a  green  reflex.  With  an 
excess  of  hydrochloric  "acid,  C^H^^HC!^  is  obtained,  a  salt 
soluble  with  a  red  colour,  but  decomposed  by  water. 


AMIDOAZO-COMPOUNDS.  41 

On  reduction  chrysoidine  splits  up,  aniline  and  triamidobenzene 
being  produced. 

C12H11N4(C8HjP)3  is  formed  by  warming  chryscidine  with 
acetic  anhydride ;  forms  yellow  prisms,  M.P.  250°  [18] . 

It  yields  a  dimethyl  derivative  on  warming  with  methyl  iodide. 

Tetramethylchrysoidine  has  been  prepared  by  the  action  of 
diazobenzene  chloride  on  tetramethylphenylenediamine. 

A  sulphonic  acid  may  be  obtained  by  treating  chrysoidine  with 
fuming  sulphuric  acid,  or  by  allowing  paradiazobenzenesulphonic 
acid  to  react  with  metaphenylenediamine. 

Chrysoidine,  which  was  discovered  by  Witt,  is  one  of  the  few 
basic  azo-dyestuffs,  and  like  all  basic  colouring-matters  dyes  cotton 
mordanted  with  tannic  acid.  Its  principal  application  is  in  cotton- 
dyeing,  especially  for  shading  purposes.  It  gives  a  yellowish- 
orange  colour. 

It  is  of  historical  interest,  as  being  the  first  azo-dyestuff  pre- 
pared by  a  direct  synthesis. 


B(  Symmetrical  Jlmidoazobenzene  [19,  20] 
Parazoaniline, 

(1)  (4)         (1)  (4) 


is  formed  by  saponification  of  the  acetyl  compound  described 
below,  and  by  reduction  of  the  compound  obtained  by  action  of 
paranitrodiazobenzene  on  aniline. 

It  forms  long,  flat,  yellow  needles.     M.P.  140°. 

It  is  sparingly  soluble  in  water  and  benzene,  easily  in  alcohol. 

The  monoacid  salts  dissolve  in  alcohol  with  a  green  colour, 
while  the  diacid  salts  give  a  red  solution. 

Acetyl  derivative  [20],  C12HnN4(C2H3O),  is  obtained  by  the 
interaction  of  aniline  and  paradiazoacetanilide  in  presence  of  a 
little  hydrochloric  acid.  M.P.  212°.  Its  salts  dissolve  with  a  red 
colour. 

Di  acetyl  derivative,  C^H^N^CgHsO^  is  formed  on  reduction 
of  paranitroacetanilide  with  zinc  powder  and  alcoholic  ammonia 
[19]  .  It  forms  yellow  needles.  M.P.  282°. 


42  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Tet  ram  ethyl  derivative  [21], 

(1)  (4)        (1)  (4) 


(Azyline),  is  formed  by  the  action  of  nitric  oxide  on  dimethyl- 
aniline,  and  by  action  of  paradiazodimethylaniline  on  the  same 
amine  [22]. 

Diphenine  of  Gerhardt  and  Laurent  [23]  and  hydrazoaniline 
of  Haarhaus  [24]  are  regarded  as  hydrazo-compounds  ;  they  are 
probably  diamidoazo-compounds,  as  they  possess  tinctorial  pro- 
perties in  a  marked  degree,  which  is  not  usual  in  hydrazo- 
compounds. 


Triamidoazobenzene. 

(1)  (4) 


r_K.. 
[2o] 


(PHENYLENE  BROWN,  VESUVINE,  BISMARK  BROWN.) 

Triamidoazobenzene  forms  brownish-yellow  warty  crystals, 
which  dissolve  sparingly  in  cold  water,  easily  in  hot  water.  M.P. 
137°.  Acids  colour  the  brownish-yellow  solution  reddish  brown, 
and  produce  diacid  salts. 

Triamidoazobenzene  is  formed  along  with  other  azo-compounds, 
on  treating  metaphenylenediamine  with  nitrous  acid.  Its  hydro- 
chloride  forms  the  principal  constituent  of  the  dyestuffs  known 
under  the  above  names.  (A  more  recent  view  is  that  Bismark 
brown  consists  partly  at  least  of  a  compound  of  the  formula 

(i) 
rTJr  /N2-C6H8=(NH2)2 


which  is  to  be  regarded  as  a  metaphenylenediamine  disazometa- 
phenylenediamine.) 

With  the  exception  of  chrysoidine,  Bismark  brown  is  the  only 
basic  azo-dyestuff  in  practical  use.  It  is  used  in  dyeing  cotton  and 
leather. 

Diamidoazotoluenes.     [See  26,  27.] 


AMIDOAZO-COMPOUNDS.  43 

Benzeneamidoazonaplitlialene  [28,  29], 


is  obtained  by  interaction  of  diazobenzene  chloride  and  #-naph- 
thylamine. 

Sulphonic  acids  may  be  obtained  by  action  of  paradiazobenzene- 
sulphonic  acid  on  a  and  /3  naphthylamine. 

A  corresponding  toluene  compound  has  been  prepared  by  action 
of  paradiazotoluene  on  a-naphthylamine  [27]  . 

The  dyestuff  known  as  orchil  substitute  or  orseilline  is  prepared 
by  action  of  paranitrodiazobenzene  on  naphthionic  acid  (a-naph- 
thylaminesulphonic  acid).  It  produces  reddish-brown  shades  on 
wool  and  is  dyed  from  an  acid  bath  [72]  . 

Amidoazonaplithalene, 
aC10H7N=:N-C10H6NH2a  [30], 

is  formed  by  action  of  nitrous  acid  on  excess  of  a-naphthyl- 
amine, and  is  best  prepared  by  mixing  a  solution  of  two  molecules 
of  a-naphthylamine  hydrochloride  with  one  molecule  of  sodium 
nitrite.  The  base  forms  reddish-brown  needles,  which  show  a 
green  reflex;  it  melts  at  175°,  and  is  sparingly  soluble  in 
alcohol,  readily  in  xylene. 

The  salts  dissolve  in  alcohol  with  a  violet  colour,  and  are 
decomposed  by  water. 

The  azo-group  is  present  in  the  a  para  position  to  the  amido- 
group.  . 

Sulphonic  acids  of  this  compound  are  obtained  by  direct  sulpho- 
nation,  or  by  combination  of  diazonaphthalenesulphonic  acid  with 
a-naphthylamine. 

A  disulphonic  acid  of  amidoazonaphthalene  is  obtained  by 
action  of  sodium  nitrite  on  naphthionic  acid;  its  constitution 
differs  from  that  of  the  above  acids,  as  the  second  a-positijn 
usually  taken  by  the  azo-group  is  occupied  by  the  sulpho-group  in 
naphthionic  acid. 

The  corresponding  /3-amidoazonaphthalene  is  obtained  in  a 
similar  manner  from  /3-naphthylamine  ;  it  melts  at  156°,  and  is 
a  slightly  weaker  base. 

Mixed  amidoazonaphthalenes  have  also  been  prepared. 


44  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


II.  OXYAZO-COMPOUNDS. 

Oxyazolenzene  [31,  32,  33]. 

(1)  (4) 

C6H5-N=N-C6H4OH. 

(Phenoldiazobenzene.} 

Oxyazobenzene  is  prepared  by  interaction  of  diazobenzene 
chloride  and  phenol-sodium  [32],  and  is  also  formed  by  action  of 
barium  carbonate  on  salts  of  diazobenzene  [31]. 

It  may  further  be  obtained  by  treating  the  isomeric  azoxy- 
benzene  with  sulphuric  acid  [34],  and  by  the  action  of  nitroso- 
phenol  on  aniline  [33]. 

It  forms  needles,  M.P.  151°;  it  is  slightly  soluble  in  water, 
easily  in  alkalies  and  in  alcohol. 

Parasulphonic  acid  — 

(1)  (4)        (1) 


may  be  obtained  by  direct  sulphonation,  or  by  action  of  paradi- 
azobenzenesulphonic  acid  on  phenol-sodium. 

This  compound  was  formerly  in  commerce  as  Tropaolin  Y,  but 
owing  to  its  dull  brownish  shade  was  soon  displaced.  An  isomeric 
metasulphonic  acid  is  formed  by  action  of  metadiazobenzenesul- 
phonic  acid  on  phenol-sodium  [36]  . 


Dioxyazobenzene  [35]. 

a.   Unsymmetrical -. — 

(i) 

/OH 

C6H5N  =  N-C6H3<(3) 
OH 

This  compound  is  prepared  by  action  of  diazobenzene  chloride 
on  resorcin  in  presence  of  an  alkali. 

It  forms  red  needles,  M.P.  161° ;  and  is  soluble  in  alcohol,  ether, 
and  alkalies. 


OXYAZO-COMPOUNDS.  45 

Parasul phonic  Acid. 
HS03-C6H4-N=N-C6H3°g. 

(TKOPAOLIN  O.) 

This  dyestuff  is  prepared  by  action  of  paradiazobenzenesulphonic 
acid  on  resorcin  [36,  37],  and  is  also  formed  by  sulphonation  of 
dioxyazobenzene  [37]. 

The  free  acid  forms  needles,  which  appear  almost  black  with  a 
greenish  lustre  by  reflected  light,  and  red  by  transmitted  light.  It 
is  a  strong  acid,  capable  of  liberating  hydrochloric  acid  from  a 
solution  of  common  salt,  thereby  forming  a  sodium  salt. 

The  salts  are  orange-yellow,  and  are  only  decomposed  by  con- 
centrated hydrochloric  acid  or  by  dilute  sulphuric  acid. 

Tropaolin  O  is  a  strong  dyestuff,  producing  a  fine  golden- 
yellow  shade  on  wool  and  silk,  being  dyed  from  an  acid  bath.  It 
was  formerly  used  in  silk-dyeing. 

The  metasulphonic  acid  is  obtained  from  metadiazobenzene- 
sulphonic  acid  and  resorcin  [36] . 

/3.  Symmetrical  dioxyazobenzenes  (AZQPHENOLS)  [38]  : — 

a.  Para-azophenol 

is  formed  on  melting  paranitro-  or  nitrosophenol   with  potash, 
M.P.  204°. 

b.  Ortho-azophenol 

is  formed  similarly  from  orthonitrophenol,  M.P.  171°. 

Oxyazobenzenetoluene  [33], 
CH3C6H4-N=N-C6H4OH, 

(Phenolazotoluene.) 
is  obtained  from  nitrosophenol  and  paratoluidine,  M.P.  151°. 

Cumeneazoresorcin^ 
(CH3)3C6H2-N  =  N-C6H3(OH)2, 
from  diazocumene  and  resorcin  [39],  M.P.  199°. 


46  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Amido-oxyazolenzene  [40], 

H2NC6H4-N  =  N-C6H4(6H)  (M.P.  168°), 
is  obtained  by  saponification  of  the  acetyl- compound 

C2H3ONH-C6H4-N=N-C6H4OH  (M.P.  208°), 

•which  is  prepared  by  interaction  of  phenol-sodium  and  the  diazo- 
compound  from  monoacetylmetaphenylenediamine. 

Oxyazo-compounds  are  also  obtained  by  action  of  diazo-com- 
pounds  on  the  isomeric  cresols  [39,  41,  42] . 

a-Azonaplithalene-resorcin  [46], 

C10H7-N=N-C6H3(OH)2, 

forms  red  needles,  M.P.  about  200°. 

NAPHTHOLAZO-DYESTUFFS. 

These  dyes  belong  to  the  oxyazo  series,  and  have  within  the  last 
ten  years  attained  enormous  importance,  on  account  of  the  beauty 
of  their  shades  and  their  strong  tinctorial  properties.  For  these, 
and  other  reasons,  they  are  worthy  of  being  studied  as  a  separate 
class. 

The  isomeric  naphthols  combine  with  all  diazo-compounds,  pro- 
ducing azo-compounds,  and  with  a-naphthol 


the  azo-chain  enters  into  the  second  a-position  of  the  substituted 
ring.  This  is  exactly  analogous  to  the  formation  of  the  corre- 
sponding compounds  with  benzene  derivatives  containing  a  free 
para  position.  The  simplest  a-naphthol  azo-compounds  are  con- 
stituted as  expressed  by  the  following  formula : 


OXYAZO-COMPOUNDS. 
OH 


47 


/3-naphthol 


has  no  free  para  position  and  the  azo-group  enters  in  the  ortho 
position,  viz.  in  the  adjacent  a-position : 


The  case  is  different  when  these  positions  are  already  occupied 
by  other  groups,  for  example,  by  the  sulpho-group.  With  a-naph- 
tholthe  azo-chain  enters  into  the  adjacent /3-position;  for  instance, 
with  a-naphtholsulphonic  acid  azo-compounds  of  the  general 
formula 

OH 


3— N=N— 


are  formed. 


48  CHEMISTRY  OF  ORGANIC  DYESTUFFS, 

The  formula  with  /3-naphthol  : 


is  probably  correct,  but  has  not  been  proved  to  be  absolutely 
certain.  In  general,  azo-compounds  containing  the  chromophoric 
and  auxochromic  groups  in  the  ortho  position  are  far  more  valu- 
able as  dyes  than  their  allies  of  the  para-series. 

The  latter  have  the  undesirable  property  of  altering  their  shade 
on  treatment  with  alkalies  or  acids  in  a  much  higher  degree  than 
the  former  compounds.  This  applies  equally  to  oxy-  and  amido- 
azo-compounds,,  especially  those  of  the  naphthol  series. 

For  this  reason  /3-naphthol  gives  more  useful  dyestuffs  than  a- 
naphthol. 

The  derivatives  of  the  latter  exhibit  striking  changes  in  colour 
on  treating  with  alkalies. 

If,  however,  the  para  position  in  a-naphthol  is  substituted,  as 
in  the  a  o-sulphonic  acid,  the  azo-group  enters  in  the  j3-  (ortho) 
position,  and  stable  and  useful  dyes  are  obtained.  Diazo-compounds 
are  capable  of  reacting  on  j£-naphthol  once,  while  a-naphthol,  like 
phenol,  reacts  with  two  molecules  of  a  diazo-compound.  In  the 
resulting  dis-azo  bodies  the  second  azo-group  is  probably  in  the 
@  1 -position,  as  expressed  in  the  following  formula  : 

OH 


The  naphthol  azo-dyes  are  almost  exclusively  applied  in  form  of 
their  sulphonic  acids.     These  may  be  obtained  by  combination  of 


OXYAZO-COMPOUNDS.  49 

sulphonated  diazo-corapounds  with  naphthols,  or  of  diazo-com- 
pounds  with  naphtholsulphonic  acids. 

The  sulpho-group  of  the  diazo-compound  has  little  or  no  influ- 
ence in  the  shade  of  the  dyestuff,  but  the  isomeric  naphtholsul- 
phonic acids  are  capable  of  giving  totally  different  dyestuffs  with 
the  same  diazo-compound.  In  most  cases  this  may  be  attributed 
to  the  different  positions  of  the  azo-group  already  mentioned.  Tt 
is  necessary  for  a  correct  comprehension  of  the  following  dyestuffs 
to  consider  the  principal  naphtholsulphonic  acids  somewhat  more 
closely,  for  although  our  knowledge  in  this  direction  is  incomplete, 
many  valuable  researches  have  been  made  in  recent  years,  of  which 
those  of  Armstrong  are  especially  worthy  of  mention. 

At  present  three  monosulphonic  acids  have  been  obtained  from 
a-naphthol,  but  the  constitution  of  only  one  of  these  is  known  with 
any  degree  of  certainty.  This  is  the  a  a-acid  prepared  by  Nevile 
and  \frinther,  and  studied  more  closely  by  Witt.  It  is  obtained  by 
decomposition  of  the  diazo-compound  of  naphthionic  acid  with 
water,  and  from  its  method  of  formation  is  constituted  according 
to  the  formula  : 

OH 


This  formula  agrees  well  with  the  nature  of  the  dyestuffs 
obtained  from  this  acid ;  they  are  totally  different  to  the  simple 
a-naphthol  dyes,  as  the  azo-group  enters  in  the  /3  1  position  and 
not  in  the  a  2. 

The  dyestuffs  from  a-naphthol  and  diazo-compounds  of  the 
benzene  series  are  orange  or  brown,  while  those  from  the  a  a-acid 
are  mostly  of  a  beautiful  ponceau-red  tone. 

A  second  acid  was  prepared  by  Schaeffer,  in  1869,  who  probably 
obtained  it  mixed  with  the  a  a- acid. 

Schaeffer' s  acid  is  obtained  along  with  the  latter  acid  by  heating 
a-naphthol  with  concentrated  sulphuric  acid  on  the  water-bath. 
It  differs  from  the  a  a-acid  by  the  sparing  solubility  of  its  sodium- 
salt  in  alcohol,  and  more  especially  by  the  dyestuffs  it  yields.  These 
are  analogous  to  the  corresponding  a-naphthol  derivatives,  and 
therefore  very  probably  para-compounds. 


50  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

The  acid  has  probably  the  constitution  expressed  by  the  follow- 
ing formula : 


as  it  yields  dinitronaphthol  on  treating  with  nitric  acid,  and  phthalic 
acid  on  oxidation. 

A  third  acid  has  been  prepared  by  Baum,  but  little  is  known  of 
its  constitution.  [Patent,  1883,  No.  3498,  Provisional  Specifi- 
cation.] 

Glaus  and  Oehler  have  examined  an  acid  [75]  to  which  they 
ascribe  the  constitution  ^  a2,  but  it  is  doubtful  whether  it  is  iden- 
tical with  the  Schaeffer  or  with  the  Nevile-Winther  acid. 

It  may  be  as  well  to  take  this  opportunity  of  remarking  that  a 
method  often  used  for  determining  the  constitution  of  naphthol- 
sulphonic  acids  appears  not  to  be  trustworthy,  as  molecular  changes, 
which  occur  so  frequently  in  the  naphthalene  series,  appear  to  take 
place  here  also.  This  is  the  method  depending  on  the  conversion 
of  the  acids  into  chloronaphthalenes  by  means  of  phosphorus 
pentachloride.  Indeed  the  results  so  obtained  often  differ  from 
all  others. 

The  Schoellkopf  Aniline  Co.  have  patented  an  acid  obtained 
by  nitration  of  a-naphthalenemonosulphonic  acid,  reduction  to 
amido-acid,  and  conversion  into  naphtholsulphonic  acid  by  the 
diazo-reaction.  It  is  so  far  characteristic  as  it  gives  a  scarlet  with 
diazotoluene,  while  its  isomers  give  oranges.  [D.P.  15871.] 

a-naphthol  also  yields  a  disulphonic  acid  (?),  and  a  trisulphonic, 
which,  however,  have  no  importance  in  the  manufacture  of  azo- 
dyes. 

/3-naphthol,  on  treating  with  sulphuric  acid,  gives  in  the  first 
instance  three  monosulphonic  acids. 

One  of  these  (the  a-sulphonic  acid  or  crocem-acid)  is  best  ob- 
tained at  a  low  temperature.  By  further  heating  with  sulphuric 
acid  it  goes  over  into  the  /3-  or  Schaeffer' s  acid,  which  was  pre- 
pared by  Schaeffer  a  long  time  ago.  These  acids  are  distinguished 


OXYAZO-COMPOUNDS.  51 

principally  by  the    different    solubilities  of  their  disodium  com- 
pounds : 

CioH6<ONa    . 

The  basic  salt  of  the  a-acid  is  easily  soluble  in  hot  alcohol, 
while  that  of  the  Schaeffer  acid  is  almost  insoluble. 

The  third  acid,  which  has  only  recently  been  identified  by  its 
conversion  into  the  corresponding  /3-naphthylaminesulphonic 
acid,  is  identical  with  the  F-  or  S-acid.  [Green :  B.  B.  1889, 
p.  721.] 

From  the  facts  that  azo-dyes  from  Schaeffer's  acid  differ  but  little 
in  shade  and  solubility  from  those  obtained  from  /3-naphthol,  and 
that  simple  /3-naphthol  azo-compounds  on  sulphonation  always 
yield  derivatives  of  Schaeffer's  acid,  and  never  those  of  croce'in- 
acid,  it  may  naturally  be  concluded  that  the  azo-group  enters  in 
the  same  position  both  in  /3-naphthol  and  in  Schaeffer's  acid.  This 
is  the  a:  position. 

The  behaviour  of  the  a-acid  is  totally  different.  The  dyestuffs 
do  not  resemble  those  from  Schaeffer's  acid  and  /3-naphthol  in  the 
least,  either  as  regards  shade  or  solubility.  Further,  this  acid  may 
easily  be  converted  into  a  dinitro-compound  with  nitric  acid,  and 
this  is  not  the  case  with  either  /3-naphthol  or  Schaeffer's  acid. 
Another  striking  property  of  the  a-acid  is  that  its  combination  with 
diazo-compounds  takes  place  with  much  more  difficulty  than  is 
experienced  with  Schaeffer's  acid.  Its  constitution  is  therefore 


justifying  the  designation  /3-naphthol-a-monosulphonic  acid  for 
this  acid.  The  conversion  of  the  corresponding  /3-naph thylamine- 
sulphonic  acid  into  a-naphthalenesulphonic  acid  also  shows  that 
it  is  really  an  a-acid. 

Schaeffer's  acid  yields  sulphophthalic  acid  on  oxidation,  showing 
that  the  hydroxyl  and  sulpho-groups  are  in  different  rings. 

E2 


52 


CHEMISTRY  OF  ORGANIC  DYESTUFtfS. 


Noelting   ascribes   the   following    constitution    to   Schaeffer's 
acid  : 


OH 


/3HS03 


A  third  sulphonic  acid  is  that  of  Cassella  and  Co.,  prepared  by 
heating  naphthalene-a-disulphonic  acid  with  caustic  alkali. 

This  acid  is  technically  known  as  F-acid,  and  is  identical  with 
the  acid  prepared  by  the  diazo-reaction  from  Bayer's  /3-naphthyl- 
amine-8-sulphonic  acid. 

Without  doubt  it  has  the  constitution : 


SCXH 


It  is  without  importance  for  preparing  azo-dyes. 

Of  the  /3-naphtholdisulphonic  acids/  three  are  used  in  the 
colour-industry  [73,  74].  Two  of  these  are  formed  by  energetic 
action  of  sulphuric  acid  on  /3-naphthol,  and  may  be  separated  by 
taking  advantage  of  the  different  solubilities  of  their  sodium  salts 
in  alcohol  or  in  concentrated  salt-solution. 

The  acid  soluble  in  alcohol  and  salt-solution  (G-acid  of  Meister, 
Lucius,  and  Briining,  7-acid  of  Cassella  and  Co.)  behaves  very  like 
./3-naphthol-a-monosnlphonic  acid  (crocein  acid),  and  must  be 
regarded  as  a  derivative  of  the  latter,  as  it  is  formed  quantitatively 
on  further  sulphonation  of  crocein  acid.  It  may  also  be  obtained 
from  Schaeffer's  acid  (this  is  contradicted  by  some  chemists),  and 
Armstrong  gives  it  the  following  formula  : — 

HS03 


HSO 


OXYAZO-COMPOUNDS.  53 

The  azo-dyes  from  G-acid  are  yellowish  and  easily  soluble,  and 
are  very  similar  to  those  from  the  a-monosulphonic  acid. 

The  disulphonic  acid  from  the  sodium  salt,  sparingly  soluble  in 
alcohol  and  salt-solution  (R-acid,  Meister,  Lucius,  and  Briining), 
gives  dyestuffs  of  considerably  bluer  shade,  and  also  more  diffi- 
cultly soluble.  They  are,  however,  very  important. 

This  R-acid  is  best  obtained  by  further  sulphonation  of  Schaeffer's 
acid,  and  it  is  also  stated  that  G-acid  is  converted  into  R-acid  on 
heating  with  sulphonic  acid.  The  constitution  of  the  R-acid  is 
expressed  by  the  formula  : — 


SOHk          A         /S°3H 


Another  disulphonic  acid,  /3-naphthol-S- disulphonic  acid  is 
prepared  by  further  sulphonation  of  the  F-acid.  It  has  the  con- 
stitution 


S(XH 


A  /3-naphtholtrisulphonic  acid  is  obtained  by  sulphonation  of 
/3-naphthol  with  fuming  sulphuric  acid  at  a  high  temperature.  It 
has  been  used  for  the  preparation  of  azo-colours. 


Azobenzene-a-napht7wl  [1], 
C6H5-N  =  N-C10H6OHa, 

is  prepared  by  action  of  diazobenzene  chloride  on  an  alkaline 
solution  of  /3-naphthol.  It  forms  yellow  leaflets,  which  dissolve 
in  alkalies  with  a  violet  colour. 


54  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


Monosulphonic  Acid  [11]. 

(I)  (4) 

HSO3-C6H4-N  =  N-C10H6OH  a. 
(ORANGE  I.  TEOPAOLIN  OOO  No.  1.) 

This  dyestuff  is  prepared  by  action  of  paradiazobenzene- 
sulphonic  acid  on  a-naphthol.  The  free  acid  forms  almost  black 
leaflets,  with  a  green  reflex,  which  dissolve  in  concentrated 
sulphuric  acid  with  a  violet  coloration.  Its  alkali  salts  are  orange- 
yellow,  and  dissolve  easily  in  water.  The  solutions  become  red 
with  excess  of  alkali  (distinction  from  /3-naphthol  dyestuffs) . 

The  sodium  salt  is  used  in  dyeing  under  the  above  names. 

It  dyes  wool  and  silk  in  an  acid  bath,  producing  an  orange 
shade,  which  is  somewhat  redder  and  not  so  bright  as  that  obtained 
with  the  corresponding  /3-naphthol  orange.  The  calcium  salt  is 
amorphous  and  insoluble.  Owing  to  the  sensitiveness  which  these 
dyestuffs  exhibit  towards  alkalies,  the  /3-naphthol  derivatives  are  of 
considerably  more  importance. 

Azobenzene-ft-naphtlwl  [1]. 

C6H5N=N-C10H6OH. 

Yellow  leaflets,  insoluble  in  alkalies. 

Monosulphonic  Acids. 

(1)  (4) 

i.     HS03-C6H4-N=N-C10H6OH/3. 

(ORANGE  II.  TROPAOLIN  OOO  No.  %,) 

From  paradiazobenzenesulphonic  acid  and  /3-naphthol.  The 
acid  forms  orange-yellow  leaflets,  soluble  in  water.  The  crystals 
on  drying  lose  water  and  fall  to  a  powder  resembling  red  lead. 
The  alkali  salts  are  similar  to  the  acid,  and  are  unchanged  by 
excess  of  alkali  (distinction  from  a-naphthol  dyestufts).  Its 
calcium  salt  dissolves  sparingly,  the  barium  salt  not  at  all.  The 
compound  dissolves  in  concentrated  sulphuric  acid  with  a  magenta- 
red  colour.  On  wool  and  silk  it  gives  a  beautiful  orange,  and  is 
one  of  the  most  important  azo-dyes. 


OXYAZO-COMPOUNDS.  55 

ii.     C6H5-N  =  N-C10H5OHHS03. 

(CKOCEIN  OKANGE.) 

From  diazobenzene  and  Schaeffer's  /3-naphtholmonosulphonic 
acid  (/3-acid).  The  shade  of  the  dyestuff  is  somewhat  yellower 
than  that  of  the  former.  It  gives  an  orange-yellow  solution  with 
concentrated  sulphuric  acid. 

Disulphonic  Acids. 

XHS03), 
C6H5-N=N-C10H4C.     ^ 

Uxi 

ORANGE  G. 

Is  obtained  by  the  action  of  diazobenzene  on  /3-naphtholdisul- 
phonic  acid  (the  modification  Gr,  soluble  in  alcohol).  It  is  a 
yellowish-orange  dyestuff,  which  gives  an  orange-yellow  solution 
with  concentrated  sulphuric  acid. 

SCAKLET  2  G. 

This  dyestuff  is  an  isomer  of  the  above,  prepared  by  action  of 
diazobenzene  chloride  on  the  R  modification  of  /3-naptholdisul- 
phonic  acid. 

Amidoazobfinzene-fi-naplitholdisulphonic  Acid. 

CD  (4)  (HSO3)2 


May  be  obtained  by  saponificaticn  of  its  acetyl  derivative,  ana  by 
combination  of  /3-naphtholdisulphonic  acid  (R)  with  paradiazo- 
aniline  [44]  (from  paraphenylenediamine  and  one  mol.  HNO2). 
It  forms  brownish-yellow  leaflets,  which  dissolve  in  alkalies  with  a 
violet  colour,  becoming  red  with  excess  of  alkali. 

Acetyl  derivative  :  — 


C2H30  .  HN-C6H4-N2-C10H4       ft         '   [43]. 


56  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

From  p-diazoacetanilid  and  naphtholdisul  phonic  acid;  forms  red 
leaflets. 

Dyestuffs  obtained  by  combination  of  the  diazotoluenes  and 
their  sulphonic  acids  with  /3-naphthol  and  its  sulphonic  acids  are 
also  of  technical  value. 


AZO-DYES  FROM  /3-NAPHTHOLDISULPHONIC  ACIDS  AND  THE 
HIGHER  HOMOLOGUES  OF  DlAZOBENZENE  [45]. 

It  has  already  been  remarked  on  p.  53  that  the  isomeric 
disulphonic  acids  of  /3-naphthol  give  dyes  of  totally  different 
shades  with  diazo-compounds.  This  is  probably  caused  by  the 
azo-group  entering  in  a  different  position  in  the  naphthalene 
nucleus.  This  property  is  made  use  of  in  the  colour-industry. 
The  acid  corresponding  to  the  sodium  salt  soluble  in  alcohol 
(G-acid,  Meister,  Lucius,  and  Bruning)  gives  orange-yellow  dyes 
with  diazo-compounds  of  the  benzene  series,  and  scarlets  with 
those  of  the  naphthalene  series;  while  the  R-acid  (Meister, 
Lucius,  and  Bruning),  from  the  sodium  salt  insoluble  in  alcohol, 
gives  red  dye-stuffs  with  the  diazo-compounds  of  the  benzene 
series,  varying  in  depth  according  to  the  molecular  weight  of  the 
latter  [45]. 

The  R-acid,  when  combined  with  the  diazo-compounds  of  the 
xylenes  and  higher  homologues  of  benzene,  gives  rise  to  a  series 
of  scarlet  dyes,  which  have  a  wide  application  in  wool-dyeing 
under  the  names  Ponceau  R,  RR,  RRR,  and  G.  a-diazonaphtha- 
lene  gives  a  deep  claret-red  (Bordeaux  B).  With  diazonaphthalene- 
sulphonic  acid  and  R-acid,  a  colouring-matter  known  as  "  Ama- 
ranth "  is  obtained.  Orthodiazoanisol  and  its  homologues  give  fine 
red  dyestuffs  known  commercially  as  Coccinines. 

The  dyes  from  diazo-compounds  of  the  benzene  series  (Pon- 
ceaux  R,  RR,  RRR,  and  Coccinines)  form  scarlet  powders,  which 
dissolve  in  strong  sulphuric  acid  with  a  red  colour.  They  give 
crystalline  calcium  salts  which  are  soluble  in  hot  water.  Dye- 
stuffs  containing  naphthalene  rests  on  both  sides  dissolve  in 
sulphuric  acid  with  blue  or  violet  colour. 


OXYAZO-COMPOUNDS.  57 

The  following  Table  contains  the  most  important  dyestuffs 
prepared  from  the  naphtholdisulphonic  acids,  excluding  those 
belonging  to  the  tetrazo  class,  which  are  mentioned  later : — 

Ponceau  2  G    (Meister,    Lucius,     &  K-acid  and  diazobenzene. 

Briining)    

„       R  (Badische  Aniline-  und  So-  R-acid  and  diazopara-  and   metaxy- 

dafab.).  lene  (from  coml.  xylidine). 

„      2  It  (Actienges  f.  Aniline)  .  .  R-acid  and  diazometaxylene  (pure). 

„       3R  (Meister,  Lucius,  &  Briin-  R-acid  and  diazoethylnietaxy lene). 

ing)    

„      3  R  (Bad.  Aniline-  und  So-  R-acid  and  diazopseudocumene. 

dafab.). 

„      4  R  (Actienges  f.  Aniline)  . .  Do. 

„      2  R  (Meister,  Lucius,  &  Briin-  Do. 

ing)   

Bordeaux  B  (do.) R-acid  and  diazonaphthalene. 

Amaranth  (Cassella  &  Co.)    R-acid  and  a-diazonaphthalene-sulph. 

acid. 

Bordeaux  S(Meister,Lucius,&Briining)  Do. 

Coccinin  (Meister.  Lucius,  &  Briining)  R-acid  and  diazoanisol. 

Pheuetol  Red  (do.) Do.  and  diazophenetol. 

Anisol  Red  (do.) Do.  and  homologues. 

Orange  G  (Meister,  Lucius,  &  Briining)  G-acid  and  diazobenzene. 

Ponceau  2  G  (Bad.  Anil.  &  Sodaf.)  . .  Do.  and  diazopseudocumene. 

Crystal  Ponceau  (Cassella  &  Co.) ....  Do.  and  a-diazonaphtkalene. 

a.~Azonaphthalene~P"naphthoL 

^ 
C10H7  — N— N2  —  C10H6OH  (0-,3-oxyazonaphthalene) . 

Is  obtained  by  interaction  of  a-diazonaphthalene  chloride  and  /3- 
naphthol. 

Monosutphonic  Acid  [47 J. 

HS03C10H6~N=N-C10H6OH. 

(FAST  KED,  ROCCELLINE.) 

This  is  obtained  by  the  action  of  a-diazonaphthalenesulphonic 
acid  on  /3-naphthol. 

The  acid  and  its  sodium  salt  both  form  brown  needles,  sparingly 
soluble  in  cold  water,  easily  in  hot,  separating  from  the  hot 
solution  as  gelatinous  precipitates.  The  calcium  and  barium 
salts  are  insoluble  and  amorphous.  The  compound  possesses 


58  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

very  strong  tinctorial  properties,  dyeing  wool  and  silk  red.  The 
shade  is  bluish  and  not  particularly  bright.  It  dissolves  in  con- 
centrated sulphuric  acid  with  violet  colour,  separating  in  brown 
flocks  on  dilution. 

Disulphonic  Acids. 
i.     C10H7N=N-C10H4J)Ifs03)2     [45]. 

a.  BORDEAUX  B  (Meister,  Lucius,  and  Briining). 

From  /9-naphtholdisulphonic  acid  (insoluble  in  alcohol)  and  a- 
diazonaphthalene.  Gives  a  blue  coloration  with  strong  sulphuric 
acid. 

1.  CRYSTAL  SCARLET  (Cassella  &  Co.). 

Obtained  in  a  similar  manner  from  a-diazonaphthalene  and  the 
G-  or  fy-disulphonic  acid  (soluble  in  alcohol).  The  sodium  salt 
crystallizes  very  easily. 

ii.  HS03 .  CIOH6-N=N-C10H5(°    '•  • 

HSO3 

CROCEIN  SCARLET  3  Bx. 

From  /3-naphthol-a-monosulphonic  acid  [48]  and  a-diazo- 
naphthalenesulphonic acid.  Is  a  beautiful  scarlet  dyestuff  which 
dissolves  in  sulphuric  acid  with  a  reddish- violet  colour. 

Sulplioazonaphthalene-a-naphtholsulphonic  Acid. 


HS03C10H6-N=N-C10H, 

(AZORUBIN.) 

This  is  prepared  by  combination  of  a-diazonaphthalenesulphonic 
acid  with  the  a-naphthol-a-sulphonic  acid  obtained  from  the  former 
acid  by  decomposition  with  water.  It  is  a  fine  bluish-red  dyestuff. 
/3-naphthylamine  and  its  sulphonic  acids  are  also  used  in  the 
manufacture  of  dyestuffs.  Oxyazonaphthalene,  obtained  from  /?- 
diazonaphthalene  and  /3-naphthol,  is  known  as  "  Carminnaphthe," 
and  is  used  in  colouring  varnishes. 

/3-naphthylaminesul phonic  acid  (Bronner's  acid),  prepared  by 
heating  Schaeffer's  /3-naphtholmonosulphonic  acid  with  ammonia, 


AZO-COMPOUNDS.  59 

gives  when  diazotised  and  combined  with  /3-naphthol,  a  dyestuff 
used  in  silk-dyeing.  With  a-naphthol-a-sulphonic  acid  the  dye 
known  as  Brilliant  Scarlet  is  obtained. 

A  dyestuff  known  as  Silk-red,  or  Scarlet  for  Silk,  is  prepared 
by  sulphonating  /3-naphthylamine  and  diazotising  the  resulting 
sulphonic  acid  and  combining  with  /3-naphthol. 


III.  AZO-DYES  FROM  DIAZOCARBONIC  ACIDS. 

Diazo-compounds  combine  with  phenols  and  amines  to  form  azo- 
compounds.  The  tinctorial  properties  of  these  bodies  are  generally 
weak;  becoming  intensified,  however,  by  converting  the  carbonic 
acids  into  their  ethers. 

Dimethylamidobenzene-azO'benzoic  Acid  [50]. 

COOHC6H4-N=N-C6H4N(CH3)2. 
Is  obtained  from  m-diazobenzoic  acid  and  dimethylaniline. 

Phenolazo-meta-benzoic  Acid  [49]. 

COOHC6H4-N  =  N-C6H4OH. 
From  diazobenzoic  acid  and  phenol.     M.P.  220°. 

o-Sulphonic  Acid. 
From  o-phenolsulphonic  acid  and  m-diazobenzoic  acid. 

Eesorcin-azo-benzoic  Acid  [49]. 
a)  3  OH 


$-Na/phthol~azo-benzoic  Acid  [49]. 

(1)  (3)  0 

COOHC6H4-N:=N-C10H6OH. 

M.P.  235°.     Ethyl  ether,  M.P.   104°  (from  diazobenzoic  acid 
ether  and  /3-naphthol)  . 


60  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Monosulphonic  Acid  [49], 
TOH 


From  m-diazobenzoic  acid  and  /3-naphtholmonosulphonic  acid. 

Disulphonic  and  trisulphonic  acids  have  also  been  prepared  by 
action  of  m-diazobenzoic  acid  and  its  sulpho-acids  on  /3-naphthol- 
disulphonic  acid.  Diazoanisic  acid,  as  well  as  the  paradiazocin- 
namic  acid  and  its  ethers  [51],  gives  red  azo-dyes  [49]  with 
naphthol  acid  and  its  sulphonic  acids. 

IV.   AZO-DERIVATIVES  FROM  CARBONIC  ACIDS  AND 
DIAZO-COMPOUNDS. 

Oxy-  and  amidocarbonic  acids  combine  with  diazo-compounds 
to  form  azo-dyes,  some  of  which  possess  the  property  of  dyeing  on 
metallic  mordants. 


Azobenzene-dimethylamidobenzoic  Acid  [50,  39]. 
CfiH,  .  N  =  N-C«H 


L  7N(CH3)2 

SXCOOH 

From  diazobenzene  and  dimethyl-m-amidobenzoic  acid.     M.P. 
125°. 

Dimethylamidolenzoic  Acid-azolenzoic  Acid. 

/COOH 
COOHC6H4-N=N-C6H/  [49]. 


By  action  of  m-diazobenzoic  acid  on  m-dimethylamidobenzoic 
acid. 

Azo-^-diamidolenzoic  Acid-p-lenzenesulphonic  Acid  [9]. 
HS03-C6H1-N=N-C6H4^. 

Is  prepared  by  action  of  p-diazobenzenesulphonic  acid  on  &-di- 
amidobenzoic  acid. 


AZO-COMPOUNDS.  61 


Azolenzenesalicylic  Add  [52]. 


(1) 
/OH  (2) 

C6H5N=N-C6H3(COOH- 
From  diazobenzene  and  salicylic  acid. 

Monosulplionic  Acid. 
From  p-diazobenzenesulphonic  acid  and  salicylic  acid  [36]. 

Azonaplithalene-salicylic  Acid  [53], 

/OH 
.,  .      C10H7N=N-C6H<cooH. 

From  a-diazonaphthalene  and  salicylic  acid.  Dyestuffs  have 
also  been  prepared  from  salicylsulphonic  acid  and  diazo-compounds 
[54].  Meta-  and  para-oxybenzoic  acids  [36],  as  well  as  oxy- 
naphthoic  acids  [55],  give  colouring-matters  with  diazo-compounds. 

The  dyes  prepared  from  salicylic  acid  mostly  possess  the 
property  of  dyeing  on  alumina,  iron,  and  chromium  mordants,  in 
a  similar  manner  to  alizarin. 

This  property,  which  is  not  met  with  in  the  meta-  and  para- 
oxy-derivatives,  seems  to  be  connected  with  the  ortho  position,  as 
in  the  quinoneoxime  dyes. 

These  mordant-dyeing  properties  are  found  in  a  much  higher 
degree  in  the  bodies  obtained  by  action  of  nitrodiazo-compounds 
on  salicylic  acid  (Germ.  Pat.  44170,  16  Nov.,  1887).  The  dye- 
stuff  from  metanitrodiazobenzene  and  salicylic  acid  comes  into 
commerce  as  Alizarin  Yellow  G,  and  produces  a  fine  yellow  lake 
with  chromium  oxide.  The  pure  dyestuff  crystallizes  from  alcohol 
in  light  yellow  needles.  M.P.  about  230°.  Its  constitution  may 
be  expressed  by  the  formula  : — 

C6H4N02-N=N-C6H3(™°H. 

It  has  been  used  to  a  certain  extent  in  calico-printing  as  a 
substitute  for  Persian-berry  extract  and  fustic  extract.  An 


62  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

isomeric   compound   from    paranitrodiazobenzene    is    known   as 
Alizarin  Yellow  R  and  gives  more  orange  shades  in  dyeing. 

These  compounds  are  also  useful  in  wool-dyeing.  The  dyeing 
process  is  simple,  as  owing  to  the  stability  of  these  compounds  the 
mordanting  with  bichromate  and  the  dyeing  may  be  effected  in  one 
bath,  a-oxynaphthoic  acid  combines  with  nitrodiazo-compounds, 
producing  brown  dyestuifs  which  possess  the  property,  like  the 
above,  of  dyeing  on  mordants. 


V.  TETRAZO-  OR  DISAZO-DYESTUFFS. 

These  bodies  differ  from  the  simple  azo-compounds  by  con- 
taining the  azo-group  —  N=N  —  more  than  once  in  the  molecule. 

According  to  their  method  of  formation  and  constitution,  these 
compounds  may  be  divided  into  different  classes.  The  first  of 
these  classes,  the  type  of  which  is  phenolbidiazobenzene  discovered 
by  Griess,  contain  the  two  azo-groups  and  the  auxochrome  amido- 
or  hydroxyl  groups  in  one  benzene  nucleus.  These  compounds 
are  obtained  by  the  action  of  diazo-compounds  on  oxy-  or  amido- 
azo-  compounds. 

A  second  class  contains  only  the  azo-groups  in  one  ring,  while 
the  auxochrome  is  in  another.  They  may  be  prepared  by  acting 
upon  amines  or  phenols  with  diazoazo-compounds  (from  amido- 
azo-bodies),  or  by  diazotisation  of  diamines  and  subsequent  com- 
bination with  amines  or  phenols  [43,  46]. 

A  third  class  of  tetrazo-dyestuffs  includes  those  prepared  from 
benzidine  and  its  analogues.  These  contain  two  azo-groups  in  two 
different  rings,  which  are  linked  to  each  other.  Tertiary  and 
quaternary  azo-compounds,  i.  e.>  those  containing  three  and  four 
azo-groups,  have  also  been  obtained. 

Phenoldisazobenzene  (Phenolbidiazobenzene)  [28,  56]. 


Is  prepared  by  treating  diazobenzene  nitrate  with  carbonate  of 
barium,  or  by  the  action  of  the  former  on  oxyazobenzene. 

It  forms  brown  leaflets,  M.P.  131°.  A  homologue,  M.P.  110°, 
may  be  obtained  from  paradiazotoluene  and  oxyazobenzene  [56]  . 


TETRAZO-COMPOUNDS.  63 

Resorcindisazolenzene  [46]. 
C6H5-N2-C6H2(OH)2-N2-C6H5. 

Two  isoraeric  compounds  are  formed  by  the  action  of  diazoben- 
zene  chloride  on  metadioxyazobenzene. 

*.  Soluble  in  alkalies,  M.P.  215°. 
13.  Insoluble  in  alkalies,  M.P.  222°. 

p-diazotoluene  reacts  with  m-dioxyazobenzene,  three  isomeric 
resorcindisazotoluenebenzenes  being  formed  [46]. 

Soluble  in  alkalies  ("'  ^  ^ 
(.«!•   Ivl.Jr.  <£4<L   . 

Insoluble  in  alkalies     /?.  M.P.  198°. 

Various  disazo-compounds  of  this  class  may  be  obtained  from 
azotolueneresorcin  (from  p-diazotoluene  and  resorcin)  by  action 
of  diazobenzene  and  diazotoluene  [46]. 

Amido-derivatives  are  produced  by  action  of  diazo-compounds 
on  unsymmetrical  diarnidoazobenzene  (chrysoi'dine)  and  its  homo- 
logues. 

For  example,  chrysoi'dine  and  diazobenzene  chloride  react  to 
form  azobenzenephenylenediaminebenzene  [57]  .  M.P.  250°. 

C6H5-N  =  N-C6H2(OH3)3-N=N-C6H5. 

Homologues  and  carbonic  acids  of  these  bodies  have  also  been 
prepared  [57,  58]. 

AZO-DYES  FKOM  AMIDOAZOCOMPOUNDS. 

Amidoazo-  compounds,  of  which  the  simplest  representative  is 
amidoazobenzene,  are  converted  into  the  corresponding  diazoazo- 
compounds,  which  latter,  like  simple  diazo-compounds,  react  with 
amines  and  phenols,  azo-dyes  being  formed.  Amidoazosulphonic 
acids  behave  in  the  same  way. 

Benzenetetrazolenzenephenol  (Tetrazobenzenephenol)  [59]. 

]  41  (4) 


Is  formed  by  interaction  of  diazoazobenzene  and  phenol.     It  may 
be  regarded  as  the  simplest  representative  of  this  class. 


64  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Benzenedisazolenzene~fi-naplithol  [60] . 

C6H5-N=N-C6H4-N=N-C10H6OH. 

( Tetrazobenzene-jS-naphth  ol.) 

From  diazoazobenzene  and  /3-naphthol.  Forms  a  brick-red 
powder  or  brown  leaflets  with  a  green  reflex.  It  is  insoluble  in 
alkalies,  sparingly  soluble  in  alcohol,  easily  in  hot  glacial  acetic 
acid.  It  gives  a  green  solution  with  concentrated  sulphuric  acid. 

The  sulphonic  acids  of  this  compound  come  into  commerce  as 
Biebrich  and  Croce'in  scarlets,  according  to  the  position  of  the 
sulpho-group. 

MonosulpJwnic  Acid  [60]. 

(1)  (4)         (1)  (4)  13 

HS03C6H4N  =  N-C6H4N=N-C10H6OH. 

From  diazoazobenzenemonosulphonic  acid  and  /3-naphthol.  The 
sodium  salt  forms  red  needles  or  an  amorphous  red  powder  which 
is  sparingly  soluble  in  cold  water,  more  easily  in  hot  water.  The 
hot  aqueous  solution  on  cooling  solidifies  to  a  gelatinous  mass. 
The  calcium  and  barium  salts  are  insoluble. 

Disulphonic  Acids. 

A.  HS03C6H4N  =  N-C6H3HS03N-N-C10H6OH  [60]. 

(BIEBRICH  SCARLET.) 

From  diazoazobenzenedisulphonic  acids  and  /3-naphthol. 
The  sodium  salt  is  easily  soluble,  and  forms  a  thick  syrup  with  a 
small  quantity  of  water,  becoming  crystalline  on  long  standing. 
It  may  be  crystallized  from  dilute  alcohol  in  red  needles.     The 
calcium  and  barium  salts  are  insoluble. 

Commercial  Biebrich  scarlet  is  generally  this  disulphonic  acid, 
sometimes  it  contains  the  monosulphonic  acid  also.  Both  give  a 
green  solution  with  concentrated  sulphuric  acid.  The  shade 
obtained  on  wool  and  silk  is  a  beautiful  cochineal  scarlet. 

B.  HS03-C6H4-N=N-C6H4N=N-C10H5OH .  HSO3. 
The  isomeric  monosulphonic  acids  of  /3-naphthol  react  with  di- 

azobenzenesulphonic  acid,  producing  dyes  which,  however,  differ 
greatly  according  to  the  position  of  the  sulpho-group.  Schaeffer's 
/3-acid  gives  dyes  of  a  bluish  shade  and  of  little  value,  while  the  a- 
acid  gives  dyestuffs  the  shade  of  which  is  much  superior  to  that  of 
Biebrich  scarlet. 


TETRAZO-COMPOUNDS.  65 

This  body  [61]  is  known  as  Crocem  Scarlet  3B,  and  although 
not  producing  fast  shades  is  used  in  cotton-dyeing.  Crocem 
Scarlet  7  B  is  a  dyestuff  of  somewhat  bluer  shade,  and  is  obtained 
from  orthoamidoazotoluenesulphonic  acid  in  the  same  manner. 
The  tetrazo-dyes  prepared  from  /3-naphthol-a-sulphonic  acid  give 
soluble  crystalline  calcium  salts,  while  those  from  the  other  acid 
give  amorphous  and  insoluble  calcium  salts. 

The  G-disulphonic  acid  behaves  similarly  to  the  a- acid,  and  its 
combination  with  diazoazobenzene,  known  as  Brilliant  Crocein  M 
(Cassella  &  Co.),  is  closely  allied  to  Crocem  3  B.  All  the  naph- 
thol  azo-dyes  derived  from  amidoazobenzene  and  its  homologues 
give  a  characteristic  reaction  on  reduction,  which  readily  serves  for 
their  recognition.  On  warming  the  alkaline  solution  with  zinc 
powder,  only  the  naphthol  or  its  sulphonic  acid  is  split  off ;  the 
amidoazo-compound  being  regenerated. 

Another  characteristic  property  of  the  compounds  of  this  class  is 
that  they  exhibit  a  peculiar  behaviour  towards  strong  sulphuric  acid. 

The  sulphonic  acids  containing  the  sulpho-groups  in  the  ben- 
zene rings  only  react  like  the  non-sulphonated  azo-compounds, 
giving  a  green  colour  with  concentrated  sulphuric  acid;  if  the 
sulpho-groups  are  in  the  naphthalene  ring,  a  violet  colour  is 
obtained ;  while,  if  both  rings  are  sulphonated,  the  colour  is  pure 
blue.  On  warming  the  green  solution  of  benzene-disazobenzene- 
/3-naphthol  in  sulphuric  acid,  the  colour  gradually  changes  to 
blue,  and  the  sulphonic  acid  formed  is  identical  with  the  one  from 
diazoazobenzenemonosulphonic  acid  and  /3-naphthol-/3-monosul- 
phonic  acid. 

a-naphthylamine  reacts  with  diazoazobenzenedisulphonic  acid 
to  produce  a  brown  dyestuff,  which  is  known  as  Archil  Brown, 
possessing,  however,  no  great  importance. 

The  combination  of  diazoazobenzenedisulphonic  acid  with 
paratolyl-/3-naphthylamine  is  known  as  Wool- Black. 

Azodibenzenephenylenediamine  [57]. 

C6H5N=N-C6H4-N=NC6H3(NH2)2. 

Is  formed  by  action  of  diazoazobenzene  chloride  on  metapheny- 
lenediamine.  It  forms  brownish-red  needles,  which  melt  at  185°, 
and  are  easily  soluble  in  chloroform,  benzene,  ether,  and  alcohol. 

F 


66 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


Azodibenzenetoluylenediamine  [57]. 


From  diazoazobenzene  chloride  and  metatoluylenediamine. 
Forms  light  brown  needles.  Sulphonic  acids  of  this  compound 
are  formed  by  using  diazoazobenzenesulphonic  acids. 

Azobenzeneazoparacresol  [42], 


Is  formed  by  action  of  diazoazobenzene  chloride  on  paracresol. 
It  forms  brown  needles,  M.P.  160°,  and  dissolves  in  sulphuric  acid 
with  violet  colour. 

The  diazoazonaphthalenes  combine  with  sulphonic  acids  of  the 
naphthols  to  form  dyestuffs,  some  of  which  are  used  on  a  large 
scale. 

Diazoazonaphthalenesulphonic  acid,  obtained  by  combination 
of  /3-naphthylaminesulphonic  acid  and  a-naphthylamine,  reacts 
with  naphtholsulphonic  acids,  producing  deep  blue  dyestuffs.  One 
of  these  comes  into  commerce  as  Blue-black  or  Azo-black,  and  dyes 
wool  a  shade  similar  to  that  with  nigrosine  [68]  . 

Other  dyestuffs  derived  from  amidoazo-compounds  are  com- 
prised in  the  following  table  :  — 


Dyestuff. 

Diazotised  Base. 

Combined  with 

Jet-Black  B.  

Benzenedisulphonic  acid 

Phenyl-  a-naphthy  lamine  . 

Fast  Violet  Bluish  .. 
Diamond  Black    .... 

Naphthylamine  Black 
D. 

Brilliant  Black  

azo-a-naphthylamine. 
j3-toluenesulphonic   acid 
azo-a-naplitliylamine. 
Salicylic     acid     azo-a- 
naphthylamine. 
Naphthalenedisulphonic 
acid  azo-a-naphthyla- 
mine. 
Aroidoazonaphthalene- 

/3-naphthol-j3-sulphonic 
acid, 
a-naphthol-a-sulphonic 
acid, 
a-naphthylamine. 

/3-naptholdisulphonic  acid 

disulphonic  acid. 

Jbv. 

Meldola  introduced   a  general   method   for  preparing  disazo- 
compounds    [62],      Nitrodiazo-compounds    are    combined    with 


TETRAZO-  COMPOUNDS.  67 

phenols  or  amines  ;  the  nitro-group  is  then  reduced,  and  the 
resulting  ami  do-compound  may  be  diazotised  and  again  combined 
with  an  amine  or  a  phenol.  As  an  example  of  the  method  of 
procedure  the  following  is  cited. 

Paranitrodiazobenzene  combines  with   diphenylamine   to   pro- 
duce : 

NO2  -  C6H4  -  N  =  N  -  C6H4NH  -  C6H5, 

This  body  on  reduction  yields  : 


This  may   be   diazotised,   and   on  combination  with   /3-naphthol 
yields  : 


The  dyestuffs  obtained  in  this  manner  belong  to  the  same  series 
as  those  prepared  with  the  diazo-compounds  of  paraphenylene- 
diamine. 

The  nitroazo-compounds  obtained  by  combination  of  nitrodiazo- 
compounds  with  primary  amines  may  be  diazotised  and  combined 
with  phenols  ;  resulting  nitrodisazo-compounds  on  reduction 
yield  amido-compounds,  which,  when  again  diazotised  and  com- 
bined with  a  phenol,  yield  tertiary  azo-compounds,  containing 
three  azo-groups. 

Paranitrodiazobenzene  combines  with  a-naphthylamine,  form- 
ing : 

N02  -  C6H4N  -  N  -  C10H6NH2  a. 

This  body,  on  diazotising  and  combining  with  /3-naphthol,  yields  : 
N02-C6H4-N=N-C10H6-N=N-C10H6OH/5. 

On  reduction  of  the  nitro-group,  and  treating  with  nitrous  acid, 
a  diazo-compound  is  obtained,  which  with  /3-naphthol  yields  a 
tertiary  azo-compound  :  — 

HOC10H6-N=N-C6H4N=N-C10H6-N=NC10H6OH/3. 

Numerous  azo-compounds  were  prepared  in  an  analogous 
manner,  and  for  these  reference  must  be  made  to  the  original 
article  [6.2]. 


68  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


AZO-DYES  FROM  BENZIDINE  AND  ANALOGOUS  BASES. 

The  tetrazo-compounds  obtained  from  benzidine  and  similar 
bases  combine  with  phenols  and  amines  to  produce  yellow,  red, 
blue,  and  violet  dyestuffs.  These  have  attained  considerable 
importance  on  account  of  their  remarkable  property  of  dyeing  (in 
form  of  alkali  salts)  on  unmordanted  vegetable  fibres. 

The  credit  of  this  discovery  belongs  to  P.  Griess,  who  first 
remarked  on  it  in  his  English  patent  (1884,  No.  1099). 

Tetrazodiphenyl  combines  with  naphthionic  acid,  producing  a 
dyestuff  :  — 

C6H4N2  —  C10 


which  has  considerable  application  under  the  name  "Congo 
Red"  [64]. 

The  free  sulphonic  acid  is  blue,  the  salts  are  scarlet,  and  give  the 
same  shade  on  cotton.  These  shades,  though  fast  to  soap,  are 
unfortunately  turned  blue  by  weak  acids.  This  property  is  less 
marked  in  the  dyestuff  known  as  Benzopurpurine  B.  It  is 
obtained  [69]  from  tetrazoditolyl  (obtained  from  o-tolidine  and 
nitrous  acid)  and  the  /3-naphthylaminesulphonic  acid,  obtained 
by  Bronner  from  Schaeffer's  /3-naphtholsulphonic  acid  and 
ammonia. 

It  will  be  of  interest,  before  entering  into  the  consideration  of 
these  dyestuffs,  to  examine  the  constitution  of  the  naphthylamine- 
sul  phonic  acids. 

The  sulphonic  acids  of  a-  and  /3-naphthylamine  are  used  for 
production  of  azo-dyes  in  general,  their  principal  application  being 
in  the  manufacture  of  the  direct-dyeing  cotton-colours. 

They  are  produced  technically  by  two  methods,  either  by  direct 
sulphonation  of  the  naphthylamines  or  by  heating  the  naphthol- 
sulphonic  acids  with  ammonia  (i.e.,  a  compound  yielding  ammonia 
on  heating). 


TETRAZO-COMPOUNDS.  69 

As  the  naplithylaminesulphonic  acids  are  very  numerous,  only 
those  of  technical  value  will  be  considered  here. 

Only  one  of  the  sulphonic  acids  of  a-naphthylamine,  the  so- 
called  naphthionic  acid,  is  of  importance. 


I.  Sulphonic  Acids  of  u-naphthylamine. 
Naphthionic  acid,  C10H6^Q  i,, 

NH. 


This  acid  is  prepared  by  heating  one  part  of  a-naphthylamine 
with  three  to  five  parts  of  concentrated  sulphuric  acid  at  100°,  or 
by  heating  a-naphthylamine  sulphate  to  180°-200°. 

II.  Sulphonic  Acids  of  p-naphthylamine. 

By  the  action  of  concentrated  sulphuric  acid  on  /3-naphthyl- 
amine  two  monosulphonic  acids  are  first  formed,  /3-naphthylamine- 
a-sulphonic  acid  (corresponding  to  the  croce'm  acid  from  /3-naph- 
thol),  and  the  ^-naphthylamine-7-sulphonic  acid. 

At  a  higher  temperature  two  other  acids  are  formed,  the 
/3-naphthylainine-y8-sulphonic  acid  (Bronner's  acid  corresponding 
to  the  Schaeffer  acid  from  /3-naphthol),  and  /3-naphthlyamine- 
F-sulphonic  acid,  corresponding  to  the  F-acid  from  /3-naphthol. 
The  ft-  and  F-acids  are  not  products  of  direct  sulphonation,  but 
result  from  a  molecular  change  in  the  a-  and  7-acids,  as  both 
these  acids,  when  heated  with  sulphuric  acid,  go  over  into  a 
mixture  of  Bronner  and  F-acid.  This  mixture  was  termed  S-acicl, 
and  its  discoverers,  Bayer  and  Duisberg  [76],  and  somewhat  later 
Weinberg  [77],  showed  that  it  could  be  split  up  into  two  acids — the 
Bronner  and  the  F-acids.  These  /3-naphthylaminesulphonic  acids 
may  also  be  produced  by  heating  the  corresponding  naphthol- 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


sulphonic  acids  with  ammonia  (i.  e.,  a  compound  yielding  ammonia 
on  heating).  In  this  manner  the  crocei'n  acid  yields  /3-napthyl- 
amine-a-sulphonic  acid,  Schaeffer's  acid  yields  /3-naphthylamine- 
/3-sulphonic  acid,  and  the  F-acid  of  Cassella  yields  the  corre- 
sponding /3-naphthylamine  F-acid. 

As  yet  the  /3-naphtholsulphonic  acid  corresponding  to  /3-naph- 
thylamine-7-sulphonic  acid  has  not  been  isolated  from  the  acids 
formed  in  sulphonating  /3-naphthol.  The  constitutions  of  the 
acids,  according  to  the  most  recent  researches,  may  be  graphically 
demonstrated  by  the  following  formulae  : — 


SO,H. 


SOJ-I 


a-acid. 


NH, 


/3-acid  (Bronner) 


NH9 


SO,H 


NIL 


S03H 

•y-acid. 


F-acid. 


Of  these  sulphonic  acids  the  /3-  and  F-acids  produce  fine  red 
dyestuffs  with  tetrazo-compounds,  while  the  a-  and  7-acids  give 
worthless  yellow  ones. 

As  has  already  been  stated,  the  /3-acid  is  used  in  the  manufac- 
ture of  Benzopurpurine  B,  and  the  F-acid  serves,  in  combination 
with  o-tetrazoditolyl,  for  production  of  a  sparingly  soluble,  bluish- 
red  dyestuff,  known  as  Diamine-red  3  B. 

If  a  mixture  of  both  acids  (i.  e.  the  so-called  S-acid)  is  used,  a 
fine  mixed  dyestuff  is  produced,  which  contains  one  molecule  of 
each  acid  linked  to  the  benzene  chains  of  the  ditolyl.  This  body 
forms  the  principal  constituent  of  the  dyestuff  known  as  Delta- 
Purpurine  5  B.  Mixed  dyestuffs  of  this  class  are  easily  obtained, 
on  account  of  a  peculiar  property  of  the  tetrazo-compounds.  The 


TETRAZO-COMPOUNDS.  71 

diazo-groups  do  not  react  simultaneously  with  the  amine  or 
phenol.  The  second  diazo-group  combines  with  some  difficulty, 
and  indeed  the  action  is  frequently  aided  by  warming.  Some  of 
these  dyestuffs  are  commercial  products. 

/3-naphtholdisulphonic  acid  (R-acid)  and  a-naphthol-a-sulphonic 
acid  both  combine  with  tetrazodiphenyl  and  tetrazoditolyl,  forming 
blue  dyestuffs,  which  dye  directly  on  unmordanted  cotton. 

The  dyestuff  from  tetrazoditolyl  and  a-naphthol-a-sulphonic 
acid  is  known  as  Azo-blue,  and  produces  reddish-blue  shades  on 
cotton,  which  are,  however,  fugitive  to  light  [63] . 

A  more  stable  dyestuff,  which  possesses  at  the  same  time  a 
purer  shade,  is  obtained  from  dimethoxylbenzidine, 

CH3OC6H3NH2 

I 
CH3OC6H3NH2 

and  a-naphthol-a-sulphonic  acid.  It  comes  into  commerce  as 
Benzazurine  [70]. 

The  combination  of  tetrazodiphenyl  and  salicylic  acid  is  known 
as  Chrysamine  [66].  It  produces  on  cotton  a  somewhat  sad 
yellow,  and  serves  principally  for  production  of  the  cream  shades 
used  as  groundwork  in  calico-printing. 

Tetrazostilbene  (obtained  by  reduction  of  azoxystilbene  and 
diazotisation  of  the  resulting  diamidostilbenej  and  its  sulphonic 
acids  yield  numerous  dyestuffs,  some  of  which  are  capable  of 
industrial  application.  Hessian  Yellow,  for  example,  is  obtained 
by  combining  tetrazostilbenedisulphonic  acid  with  salicylic  acid. 

The  dyestuffs  of  this  class  have  the  property  of  acting  to  a 
certain  extent  as  mordants  for  basic  dyestuffs,  and  cotton  dyed 
with  them  acts  with  basic  dyestuffs  as  if  prepared  with  tannic 
acid.  Frequent  application  of  this  property  is  made  in  practice. 
For  instance,  methylene  blue,  green,  &c.,  may  be  dyed  on  a  blue 
azo-dyestuff,  and  in  this  manner  the  shades  may  be  modified  at 
will. 

The  following  Table  comprises  the  principal  direct  dyes  at 
present  in  the  market : — 


72 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


Dyestu/. 

Diazotised  Baae. 

Combined  ivith 

Chrvsamine  G  

Benzidine. 

! 
1 

)) 

-    \ 

>•> 
» 
?? 

1      -        1 
1 

j> 

» 

Orthotolidine. 

v 

••      ! 
-     J 

» 

» 

» 

••     I 

2  mols.  salicylic  acid. 
1  mol.  salicylic  acid. 
1  mol.  naphthionic  acid. 
1  mol.  sulphanilic  acid. 
1  mol.  phenol. 
2  mols.  naphthionic  acid. 
1  mol.  naphthionic  acid. 
1  mol.  tt-naphtholsulphonic 
acid  N.W. 
1    mol.    /3-naphthylamine- 
disulphonic  acid  R. 
1    mol.    /3-naphthylarnine- 
monosulphonic  acid  B. 
2   mols.  /3-naphthylamine- 
fi-monosulphonic  acid. 
2   mols.    a-naphtholmono- 
sulphonic  acid  N.W. 
2    mols.    j8-naphtholdisul- 
phonic  acid  R. 
2    mols.    /3-naphtholniono- 
sulphonic  acid  B. 
2  mols.  amidonaphtholsul- 
phom'c      acid     prepared 
from  /3-naphthylamine--y- 
disulphonic  acid  by  melt- 
ing with  alkali. 
1    mol.    y-amidonaphthol- 
sulphonic  acid. 
1  mol.  salicylic  acid. 
2    mols.   •y-amidonaphthol- 
sulphonic  acid. 
2  mols.  salicylic  acid. 
1  mol.  naphthionic  acid. 
1  mol,  resorcin. 
1  mol.  naphthionic  acid. 
1  mol.  a-naphtholsulphonic 
acid  N.W, 
1     mol.    /3-naphthylamine- 
sulphonic  acid  B. 
1    mol.   /3-naphthylamine- 
disulphonic  acid  R. 
2  mols.   /8-naphthylamine- 
monosulphonic  acid  B. 
2  mols.  naphthionic  acid. 
2      mols.     naphthylamine- 
monosulphonic           acid 
(Laurent). 
1   mol.    /3-naphthylamine- 
5-monosulphonic  acid. 
1    mol.  j3-naphthylamine- 
monosulphonic  acid  B. 

Benzo-Orange  G  R  .  . 
Congo  Yellow  Paste 

Congo  Corinth  

Brilliant  Congo  G  .  . 
Deltapurp  urine  G  .  .  .  . 

Benzidine  Blue  

Bordeaux  Extra  .... 
Congo  Violet 

Diamine  Black  R  .  .  .  . 

Diamine  Fast  Red  .  . 
Diamine  Violet  N  
Chrysamine  R  

Congo  Red  4  R  
Congo  Corinth  B  

Brilliant  Congo  R  .  . 

Benzopurpurine  B  .  . 

Benzopurpurine  4  B.  . 
Benzopurpurine  6  B  .  . 

Delta-Purpurine  5  B  . 

TETRAZO-COMPOUNDS. 


73 


TABLE  (continued). 


Dyestuff. 


Diazotised  Base. 


Combined  with 


Delta-Purpurine  7 13 . 
Diamine  lied  3  B . . . 
Rosazurine  B  . 


Rosaz  urine  G 
Azo-Blue  . , 


Orthotolidine. 


Toluylene  Orange  G . . 
Toluylene  Orange  R. . 

Brilliant  Purpurine  . . 


Direct  lied    

Cotton  Red 

Sulphonazurine 

Rosazurine  BB 
Diamine  Red  NO. . . . 

Diamine  Yellow  N  . . 

Diamine  Blue  B  . . . . 

Diamiue  Blue  3  R 
Diamine  Black  B.  . .  . 

Diamine  Blue-Black  E 


Benzopurpurine  10  B 
Rosazurine    . 


Diarnidophenyltolyl. 

Orthometatolidine. 

Benzidinesulphone    di- 

sulphonic  acid. 

Benzidiuesulphone. 

Ethoxybenzidine.    - 


Diauisidine. 


^  Benzoazurine  G    , 


2  mols.  /3-naphthylamine- 

S-monosulphonic  acid. 
2  mols.  methyl-/3-naphthyl- 

amine-S-monosulphonic 

acid. 
1  niol.  methyl-/3-naphthyl- 

amine-8-monosulphonic 

acid. 

1  mol.  /3-naphthylamine-S- 
monosulphonic  acid. 

2  mols.  a-naphtholsulphonic 
acid  N.W. 

1  mol.  cresotic  acid. 

1  mol.     metatoluylenedia- 
minesulphonic  acid. 

2  mols.    metatoluylenedia- 
minesulphonic  acid. 

1  mol.  /3-naphthylamine- 
disulplionic  acid  R. 

1  mol.  naphthionic  acid. 

2  mols.  naphthionic  acid. 
2  mols.  naphthionic  acid. 

2  mols.  phenyl-/3-naphthyl- 
amine. 

2  mols.  naphthionic  acid. 

1  mol.  /3-naphthylamine- 
suiphonic  acid  B. 

1  mol.  /3-naphthylamine- 
sulphonic  acidF. 

1  mol.  salicylic  The  pro- 
acid,  duct  is  then 

1  mol  phenol.        ethylated. 

1  mol.  /3-naphthol-d-disul- 
phonic  acid. 

1  mol.     a-naphthol-a-sul- 
phonic  acid. 

2  mols.    a-naphthol-a-sul- 
phonic  acid. 

2  mols.  •y-amidonaphthol- 
monosulphonic  acid. 

1  mol.  /3-naphthol-8-disul- 
phonic  acid. 

1  mol.    y-amidonaphthol- 
sulphonic  acid. 

2  mols.  naphthionic  acid. 

2  mols.  /3-naphthylamine- 
sulphonic  acid  B. 

2  mols.  a-naphtholsul- 
phonic acid  N.W. 


74 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


TABLE  (continued). 


Dyestuff. 

Diazotised  Base. 

Combined  with 

Benzoazurine  3  G.  .  .  . 
Brilliant  Azurine  5  G 

Azo-Violet  

Dianisidine. 

n 

)) 

V 

Diamidostilbenedisul- 
phonic  acid. 
Dianiidostilbenedisul- 
phonic  acid. 
Ethylation  of 
Diamidostilbenedisul- 
phonic  acid. 
Diamidostilbenedisul- 
phonic  acid.                j 
Diamidocarbazol. 
1*5      naphthylenedia- 
mine. 
Dianiido-diphenylene. 

)) 
Diamido-azoxytoluene. 

Triamido-azobenzene. 
Benzidinedisul  phonic 
acid     disazo-a-naph- 
thylamine. 
Tolidiue  disazo-a-naph- 
thylamine. 
Benzidine     disazo-sali- 
cylic  acid  a-naphthy- 
lamine. 

2   mols.   a-naphthylamine- 
sulplionic  acid  (Cleve). 
2  niols.  dioxynaphthalene- 
nionosulphonic  acid  from 
Schollkopf's  acid. 
1  mol.  naphthionic  acid. 
1  mol.  a-naplitholsulphonic 
acid  N.W. 
2  mols.  methyl-/3-naphthyl- 
amine-S-sulphonic  acid. 
2  mols.  salicylic  acid. 

2  mols.  phenol. 

Brilliant  Yellow. 
2  mols.  /3-naphthylamine. 

1  mol.  a-naphthylamine. 
1  mol.  /3-naphthol. 
2  mols.  salicylic  acid. 
2  mols.  naphthionic  acid. 

2  mols.  naphthionic  acid. 
2  mols.  salicylic  acid. 
2   mols.    naphtholsulphonic 
acid  N.W. 
Naphthionic  acid. 
2     mols.       a-naphtholsul- 
phonic  acid  N.W. 

2      mols.     a-naphtholsul- 
phonic  acid  N.W. 
2      mols.      a-naphtholsul- 
phonic  acid  N.W. 

Heliotrope  

Hessian  Yellow  .... 
Brilliant  Yellow  
Clirysopheniue  .... 

Hessian  Purple  N  .  .  .  . 
Hessian  Violet  

Carbazol  Yellow  .... 
Naphthylene  Red  .  . 

Cotton  Yellow  . 

Saint  Denis  Red  .... 

Benzo-Brown  B 
Benzo-Blue-Black  G 

Benzo-Blue-Black  R 
Benzo-Black 

The  property  possessed  by  the  above  dyestuffs  of  becoming 
fixed  on  cotton  from  an  Alkaline  bath  (in  form  of  their  salts)  is 
not,  as  has  been  supposed,  peculiar  to  the  derivatives  of  benzidine 
and  its  analogues.  This  characteristic  is  far  more  widely  distri- 
buted, and  has  only  been  overlooked.  Nearly  all  tetrazo-com- 
pounds  may  be  fixed  to  a  slight  extent  on  cotton,  and  the  dyestuffs 
obtained  from  paraphenylenediamine  are  almost  as  capable  in 
this  respect  as  the  benzidine  derivatives. 


AZO-COMPOUNDS.  75 


Azarin  S  [67]. 

The  sodium  bisulphite  compound  of  an  azo -dyestuff,  prepared 
by  combining  dichlordiazophenol  with  /3-naphthol,  comes  into 
commerce  under  the  above  designation. 

This  azo-dyestuff,  which  is  insoluble,  has  a  fine  red  colour,  and 
possesses  the  property  of  forming  a  lake  with  alumina.  By  treat- 
ment with  sodium  bisulphite  this  body,  like  all  azo-dyestuffs, 
yields  an  unstable  sulphonic  acid,  which  is  only  slightly  coloured. 
If  this  compound  is  printed  with  aluminium  acetate,  and  steamed, 
the  sulphonic  acid  is  decomposed,  and  the  dyestuff  combines  with 
the  alumina  to  a  firmly  adhering  lake. 

Azarin  finds  its  principal  application  in  calico-printing,  and 
produces  a  fine  red  which,  though  fast  to  washing,  is  not  suffi- 
ciently fast  to  light  to  compete  with  alizarin. 

Another  azarin  is  obtained  by  combination  of  diazotised  dia- 
midooxysulphobenzide  (phenolsulphone)  with  /3-naphthol.  It  is 
also  applied  in  form  of  its  bisulphite  compound. 


Sun-Yellow. 

Another  dyestuff  closely  related  to  the  azo-compounds  is  a 
derivative  of  the  so-called  azoxystilbene.  Its  sulphonic  acids 
dye  cotton  directly  from  an  acid  bath. 

This  yellow  dyestuff  is  obtained  by  heating  paranitrotoluene- 
orthosulphonic  acid  with  alkalies.  It  yields  diamidostilbenesul- 
phonic  acid  on  reduction,  but  whether  it  is  azoxystilbene  or 
whether  a  ring-formation  between  the  methane-group  and  the 
azo- chain  has  taken  place  is  doubtful  [78,  79]. 

The  compound  in  question  is  known  as  Sun-Yellow. 


Thiotoluidines  (PEIMULINE)  [SO,  81]. 

By  action  of  sulphur  on  paratoluidine,  Merz  and  Weith  obtained 
a  base  called  thiotoluidine  (C6H3CH3NH2)2S,  M.P.  103°.  This 
reaction  takes  place  at  140°;  and  if  a  higher  proportion  of  sulphur 
and  a  more  elevated  temperature  be  employed,  two  new  thiobases 
are  formed,  one  of  which  is  known  as  dehydrothiotoluidine 


76  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

C14H12N2S,  and  the  other  is  the  mother-substance  of  primuline. 
The  salts  of  the  sulphonic  acid  of  the  latter  come  into  commerce  as 
Primuline,  Polychromine,,  &c.  Primuline  dyes  unmordanted  cotton 
directly  from  an  alkaline  bath,  but  its  principal  application  is  in 
connection  with  the  so-called  developers.  This  depends  on  the 
fact  that  primuline  contains  an  amido-group  capable  of  being  dia- 
zotised  on  the  fibre.  This  was  introduced  technically  by  Green  as 
a  method  of  producing  insoluble  azo-dyes  direct  on  the  fibre,  the 
goods  dyed  with  primuline  being  diazotised  in  a  slightly  acid  bath 
with  sodium  nitrite,  and  then  passed  into  the  various  yellow,  red, 
&c.  developers,  which  consist  of  certain  amines  and  phenols  in 
suitable  solvents. 

Erica. 

Metaxylidine  gives  similar  compounds  if  treated  with  sulphur. 
One  of  these,  M.P.  107°,  possesses  one  amido-group  capable  of 
being  diazotised,  and  certain  of  the  azo-dyes  prepared  with  it  form 
the  various  brands  of  Erica.  These  dyestuffs  have  the  remark- 
able property  of  dyeing  cotton  from  a  bath  containing  sulphate  of 
soda,  producing  pleasing  pink  shades  of  considerable  fastness. 

Erica  B  is  the  result  of  the  combination  of  dehydrothiometa- 
xylidine  with  a-naphthol-e-disulphonic  acid. 


Thiaflavine. 

The  Thioflavines,  although  not  azo-dyes,  are  closely  related  to 
Primuline,  and  may  therefore  be  described  here. 

By  action  of  methyl  chloride  on  dehydrothiotoluidine  from  the 
primuline  melt,  two  compounds  are  formed,  one  of  which  comes 
into  commerce  in  the  form  of  its  hydrochloride  as  Thioflavine  T. 
It  is  a  basic  dyestuff,  producing  fine  greenish  shades  of  yellow. 
The  second  product  of  the  reaction,  which  is  separated  from  the 
previous  one  by  means  of  its  sparing  solubility  in  dilute  hydrochloric 
acid,  yields  on  treatment  with  fuming  sulphuric  acid  a  sulphonic 
acid,  a  salt  of  which  is  sold  under  the  name  of  Thioflavine  S.  It 
is  a  substantive  dyestuff  applied  to  cotton  from  an  alkaline  bath. 

Thioflavine  T  is  a  dimethyldehydrothiotoluidine-methyl  chloride 
of  the  formula — 


AZO-COMPOUNDS.  77 

CH3     Cl 

/K 

CH3— C6H3<        ^C— C6H4— N(CH3)2HC1 ; 
\S^ 

and  Thioflavine  S  is  a  sodium  salt  of  dimethyldehydrothiotolui- 
dinesulphonic  acid,  C16H15N2S2O3Na. 


DIRECT  PRODUCTION"  OF  AZO-DYES  ON  THE  FIBRE. 

Azo-dyes  prepared  by  interaction  of  a  diazo-compound  and  a 
phenol  are  insoluble  in  water,  and  therefore  of  no  practical  value. 
For  this  reason  a  sulpho-group  is  introduced  (see  p.  84),  and  this 
produces  the  solubility  necessary  for  their  application  in  ordinary 
dyeing  processes.  These  sulphonated  azo-dyes  have  a  considerable 
affinity  for  wool  and  silk,  but  (with  the  exception  of  those  of  the 
tetrazo-series)  are  not  easily  fixed  on  cotton.  Cotton  may  be 
dyed  with  certain  azo-dyes  of  the  Crocem  series,  but  the  shades 
produced  are  not  fast  to  washing. 

The  ease  with  which  the  combination  of  a  diazo-compound  and 
a  phenol  takes  place,  and  the  purity  of  the  resulting  product, 
doubtless  led  to  the  idea  that  insoluble  azo-dyes  might  be  pro- 
duced by  direct  precipitation  on  vegetable  fibres. 

Messrs.  Holliday  were  the  first  to  make  a  practical  application 
of  the  diazo-reaction  in  this  direction,  and  in  1880  they  patented 
processes  whereby  azo-dyes  might  be  produced  on  vegetable  fibres. 
Three  alternative  methods  are  prescribed  : — 

I.  The  goods  are  impregnated  with  an  alkaline  solution  of  a 
phenol,  and  the  colour  produced  by  passage  through  a  solu- 
tion of  a  diazo-compound. 
II.  The   above    process    is   reversed,    the   diazo-solution   being 

applied  first. 

III.  The  goods  are  impregnated  with  a  mixture  of  diazo-compound 
and  phenol,  and  the  colour  developed  by  passage  through 
alkali. 

Grassier,  in  the  same  year,  brought  out  a  process  whereby  the 
use  of  acid  to  develop  the  nitrous  acid  necessary  for  diazotisation 


78  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

is  avoided.  A  mixture  of  an  amine,  sodium  nitrite,  ammonium 
chloride,  and  a  phenol  is  thickened,  and  the  goods  impregnated  or 
printed  with  the  mixture,  and  the  colour  developed  by  drying  and 
steaming.  A  shade  closely  approaching  Turkey  red  is  obtained  by 
using  a  mixture  of  xylidine  and  /3-naphthol. 

A  process  which  has  been  used  for  silk-dyeing  is  similar  to  that  of 
Messrs.  Holliday.  A  diazo-compound  in  solution  is  neutralised  by 
chalk,  and  a  phenol  (/3-naphthol)  obtained  in  a  fine  state  of  division 
by  precipitation  is  added.  On  working  the  goods  in  this  mixture, 
the  colour  is  gradually  developed  and  is  fixed  on  the  fibre. 

Messrs.  Meister,  Lucius,  and  Briining  have  recently  modified 
the  Holliday  process,  and  adopt  a  method  somewhat  resembling 
the  last  described.  It  was  found  that  the  presence  of  free  mineral 
acid  in  the  solution  of  the  diazo-compound  is  disadvantageous,  and 
that  brighter  and  more  even  shades  are  obtained  if  the  free  acid  is 
neutralised  by  addition  of  chalk,  or  replaced  by  acetic  acid,  this 
being  effected  by  addition  of  sodium  acetate.  The  goods  are 
worked  first  in  the  phenol  dissolved  in  water  in  presence  of  two 
molecules  of  caustic  soda,  dried,  passed  into  the  prepared  solution 
of  the  diazo-compound,  and  washed  till  the  wash-waters  are 
colourless. 

In  general  the  theoretical  proportions  indicated  by  equation  are 
adhered  to  in  the  preparation  of  the  diazo-solutions ;  certain  bases, 
however,  are  not  easily  soluble,  and  are  brought  into  commerce 
in  pastes  containing  25  per  cent,  of  amine  and  the  amount  of 
nitrite  necessary  for  diazotising.  The  diazo-solution  is  obtained 
by  solution  in  the  calculated  amount  of  dilute  hydrochloric  acid. 
The  red  shades  obtained  by  this  process  become  duller  on  soaping, 
with  the  exception  of  those  from  the  amidoazo-compounds.  The 
shades  obtained  from  amidoazo-compounds  are  also  faster  to 
light  than  those  from  simple  amines.  The  shades  obtained  with 
/3-naphthol  are  bright  orange-yellow  to  red,  those  from  a-naphthol 
having  a  brown  tone.  A  shade  approximating  to  Turkey  red  is 
obtained  from  /3-naphthol  and  diazotised  /3-naphthylamine. 

The  above  processes  are  purely  mechanical,  the  goods  being 
simply  impregnated  with  the  diazo-compound,  or  phenol.  Another 
group  of  methods  differs  in  an  important  respect — that  the  amine 
is  first  actually  fixed,  by  dyeing,  on  the  fibre.  It  has  already  been 
mentioned  that  primuline  (an  amine)  may  be  fixed  on  cotton, 


AZO- COMPOUNDS.  79 

diazotised  on  the  fibre,  and  new  azo-colours  produced  by  passage 
of  the  goods  through  developers,  i.  e.  solutions  of  amines  or 
phenols  capable  of  combining  with  the  diazo-compound  of  primu- 
line.  It  is  evident  that  this  method  must  be  more  advantageous 
than  those  in  which  the  diazo-compound  is  in  mere  mechanical 
incorporation  with  the  fibre,  shades  produced  by  the  latter  process 
being  more  liable  to  rub. 

Of  late  a  new  class  of  direct-dyeing  cotton -colours  has  been 
introduced.  These  contain  one  or  more  free  amido-groups  capable 
of  diazotisation,  and  are  therefore  suitable  for  direct  production  of 
azo-dyes  on  the  fibre.  Amongst  these  dyestuffs  are  Diamine  Blue- 
Black  E,  Diamine  Black  B  and  R  (see  Table).  These  dyestuffs 
are  combinations  of  diazotised  bases  of  the  Benzidine  series  with 
one  or  two  molecules  of  an  amidonaphtholsulphonic  acid,  and 
these  amido-groups,  in  the  naphthol  compound  remaining  intact, 
may  subsequently  be  diazotised. 

Cotton  is  dyed  in  a  bath  containing  Glauber's  salt  and  a  little 
soap  or  soda,  and  the  shades  produced  vary  from  dark  blue  to 
bluish  black,  about  6  per  cent,  of  dyestuff  being  necessary  to  pro- 
duce a  maximum  effect.  The  diazotising  is  effected  by  a  bath  of 
sodium  nitrite  acidified  with  hydrochloric  acid.  The  developing- 
bath  varies  according  to  the  shade  required.  Resorcin,  /3-naphthol, 
and  phenylenediamine  produce  blacks  of  various  shades ;  blues  are 
obtained  with  naphthylamine  ether ;  and  mixtures  of  these  deve- 
lopers produce  blacks  of  every  conceivable  shade. 

In  all  these  processes  depending  on  the  use  of  diazo-compounds 
the  principal  point  is  to  work  as  cold  as  possible.  Diazo-com- 
pounds decompose  with  a  slight  elevation  of  temperature,  and  are 
unstable  at  ordinary  temperatures,  and  therefore  it  is  necessary  to 
work  as  expeditiously  as  possible.  In  the  Holliday  and  allied  pro- 
cesses, where  a  diazo-compound  is  used  in  solution,  ice  is  frequently 
necessary  for  its  preservation ;  where  the  diazo-compound  is  pro- 
duced on  the  fibre,  this  is  not  of  such  great  moment. 


80  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


CHAPTER   III. 

OXYQUINOKES  AND  QUINOKEOXIMES. 

THE  quinones  belong  to  the  most  powerful  class  of  chromogens,  and 
this  is  equally  true  of  both  the  para-  and  orthoquinones.  They 
yield  actual  dyestuffs  by  introduction  of  auxochromic  groups.  The 
oxyquinones  possess  a  specially  marked  dyestuff-character,  as  the 
quinone  group  belongs  to  the  acid-forming  chromophors,  and  the 
hydroxyl  group  introduced  develops  powerful  acid  properties. 

All  the  oxyquinones  are  coloured  and  form  salts  of  still  darker 
colour.  Most  of  them  may  be  fixed  directly  on  animal  fibres,  but 
the  shades  obtained  are  weak  and  without  value. 

The  true  character  of  a  number  of  these  bodies  only  appears  in 
their  combinations  with  metallic  oxides ;  in  other  words,  the  oxy- 
quinones belong  to  the  class  of  "  mordant-dyeing  "  colouring- 
matters.  They  are  especially  distinguished  by  the  beauty  and 
fastness  of  their  metallic  lakes. 

An  interesting  property  in  connection  with  these  bodies  is 
that  only  such  oxyquinones  as  have  one  hydroxyl  group  in  the 
ortho-position  to  the  quinone-oxygen  possess  this  power  of  dyeing 
on  mordants,  and  that  in  general  it  is  necessary  to  have  simul- 
taneously two  hydroxyl-groups  in  the  ortho-position  to  each  other 
[32,  33]. 

The  rest  of  the  oxyquinones  form  coloured  metallic  salts  which 
are  often  insoluble,  but  which  do  not  possess  the  essential  pro- 
perty of  adhering  to  fibre. 

The  oxyquinones  of  the  benzene  series  contain  at  least  one 
hydroxyl  group  besides  the  quinone-oxygen,  and  so  far  as  they 
have  been  examined  are  capable  of  dyeing  on  mordants  in  a  greater 
or  less  degree.  Tetroxy quinones,  rhodizonic  acid  (dioxydiquinpyl) 
and  nitranilic  acid  (dinitrodioxyquinone)  have  great  power  in  this 


OXYQUINONES  AND  QUINONEOXIMES.  81 

direction,  while  it  is  present  to  only  a  slight  extent  in  dioxyquinone 
and  chlor-  and  bromanilic  acids. 

The  tinctorial  power  of  these  bodies  is,  however,  slight,  and  a 
dyestuff  of  sufficient  intensity  and  stability  is  only  reached  in  the 
naphthalene  series.  This  is  naphthazarin,  a  dioxyquinone  of  un- 
known constitution. 

The  quinoneoximes  closely  resemble  the  oxyquinones  in  their 
properties.  Only  compounds  derived  from  orthoquinones  are 
capable  of  fixation  on  mordants.  Mono-  or  dioximes  are  formed 
by  substitution  of  one  or  both  quinone-oxygen  atoms  in  an  ortho- 
quinone  by  the  isonitroso-group  NOH. 

Both  may  be  dyed  on  metallic  mordants,  especially  on  iron  or 
cobalt  oxide.  The  mono-oximes,  however,  are  more  useful  in  this 
respect,  and  have  for  some  time  been  applied  technically. 

Naphthazarin  ( Dioxynaphthoquinone). 
C10H402(OH)2. 

This  compound  was  discovered  by  Roussin  in  the  year  1861, 
and  for  some  time  was  thought  to  be  alizarin.  It  is  obtained  by 
heating  a-dinitronaphthalene  with  concentrated  sulphuric  acid, 
fragments  of  zinc  being  added  to  the  hot  solution.  It  sublimes  in 
brown  needles,  with  a  cantharides  lustre.  It  is  sparingly  soluble 
in  water,  easily  in  alcohol  and  glacial  acetic  acid,  with  a  red  colour. 
It  forms  a  blue  solution  with  alkalies  and  a  red  one  with  strong 
sulphuric  acid.  It  combines  with  sodium  bisulphite,  and  the  com- 
pound formed  dissolves  readily  in  water.  Naphthazarin  dyes 
excellently  on  mordanted  fibres,  giving  a  violet  on  alumina  and 
a  grey  on  chromic  oxide. 

Naphthazarin  has  recently  been  introduced  into  commerce  as 
Alizarin  Black.  The  commercial  product  is  the  bisulphite  com- 
pound, and  finds  its  principal  application  in  printing.  For  this 
purpose  it  is  mixed  with  chromium  acetate.  On  steaming  the 
bisulphite  compound  is  decomposed,  and  the  naphthazarin  com- 
bines with  the  chromic  oxide  to  form  a  firmly  adhering  lake. 

ANTHRAQUINONE  DYESTUFFS. 

Anthraquinone  itself  has  only  a  slight  yellow  colour,  while  all 
its  hydroxyl  derivatives  have  a  more  or  less  marked  colour,  gene- 
rally orange-yellow  to  red.  The  solutions  of  the  alkali-salts  are 


82  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

generally  red  or  violet.  Certain  of  these  bodies  possess  affinity  for 
animal  fibres,  and  may  be  fixed  like  acid  colours,  but  the  shades 
produced  have  no  practical  value. 

The  utility  of  these  dyestuffs  depends  solely  on  their  capability 
of  forming  insoluble  lakes  with  metallic  oxides.  These  lakes  may 
be  firmly  fixed  on  textile  fibres,  their  colour  varying  according  to 
the  nature  of  the  metal.  Indeed  the  metallic  compounds  of  these 
bodies  may  be  looked  upon  as  so  many  different  dyestuffs. 

Of  the  numerous  hydroxyl  derivatives  of  anthraquinone,  only 
those  which  have  two  hydroxyl-groups  in  the  1,  2-position  to  the 
carbonyl-group  of  anthraquinone  are  capable  of  dyeing  upon 
mordants.  In  other  words,  only  alizarin  and  its  derivatives  possess 
this  property.  As  the  number  of  anthraquinone  derivatives  is  very 
large,  we  must  necessarily  confine  ourselves  to  those  of  technical 
value. 

Alizarin  [2,  3]. 
C14H8O4. 

Alizarin  is  one  of  the  few  natural  dyestuffs  which  have  been 
prepared  synthetically,  and  is  probably  the  only  one  which  is  pre- 
pared artificially  on  the  large  scale.  It  occurs  generally  as  a 
glucoside,  ruberythric  acid  C26H28O14  [1,  2]  in  madder,  the  root 
of  Rubia  tinctorium,  and  also  in  some  other  plants. 

Ruberythric  acid  splits  up  by  boiling  with  dilute  acid,  or  by 
fermentation,  glucose  and  alizarin  being  formed. 

C26H28014  +  2H20  =  C14H804  +  2C6H1206. 

Alizarin  crystallises  in  reddish-brown  needles,  which  are  almost 
insoluble  in  water,  sparingly  soluble  in  alcohol,  more  easily  in  hot 
glacial  acetic  acid,  carbon  disulphide,  and  glycerine.  It  melts  at 
289°  to  290°  C.,  and  sublimes  at  a  higher  temperature  in  beautiful 
long  red  needles.  It  dissolves  in  alkalies  with  a  violet  colour,  and 
the  sparingly  soluble  acid  salts  may  be  precipitated  from  these  solu- 
tions by  carbonic  acid.  On  oxidation  with  nitric  acid  it  gives 
phthalic  acid,  and  by  heating  with  zinc  powder  anthracene  is 
formed.  With  the  oxides  of  aluminium,  barium,  calcium,  iron,  and 
most  of  the  heavy  metals  it  gives  characteristic  coloured  insoluble 
lakes.  The  red  alumina  lake,  the  maroon  chromium  lake,  and  the 
violet-  black  iron  lake  are  of  importance  in  dyeing. 

The  hydroxyl-groups  in  alizarin  are  in  the  adjacent  positions 


OXYQUINONES  AND  QUINONEOXIMES.  83 

to  one  carbonyl-group  of  anthraquinone,  and  its  constitution  may 
be  expressed  by  the  following  formula  [4]  : — 

CO  OH 


The  hydroxyl-hydrogen  atoms  of  alizarin  may  be  replaced  by 
alcohol  and  acid  radicals.  The  alkyl  derivatives  are  easily  obtained 
by  heating  alizarin  with  the  requisite  alkyl  iodide  in  presence  of 
caustic  alkali.  Mono-  and  di- derivatives  may  be  obtained  in  this 
manner  [5,  6]. 

Acetic  anhydride  gives  a  diacetyl  derivative,  M.P.  160°  C.  [7]. 
Chlorine  acts  on  alizarin,  forming  a  monochloralizarin ;  with 
antimony  pentachloride,  dichlor-  [8]  and  finally  tetrachlor-alizarin 
maybe  obtained.  Corresponding  bromine  derivatives  have  also 
been  prepared  [8,  9,  10] . 

On  heating  with  ammonia  in  sealed  tubes  two  isomeric  ali- 
zarin amides  (oxyamido-anthraquinones,  C14H6O2(OH)NH2)  are 
obtained.  The  principal  product  of  the  reaction  is  the  meta-com- 
pound  with  a  small  quantity  of  the  ortho. 

Sulphonic  acids  of  alizarin  have  also  been  prepared,  and  are 
met  with  in  commerce  under  the  name  of  Alizarin  Red  S. 

Alizarin  may  be  prepared  artificially  by  fusing  dibromanthra- 
quinone,  nitroanthraquinone,  or  anthraquinonesulphonic  acid  with 
potash  or  soda  [3]  ;  also  by  condensation  of  phthalic  acid  with 
pyrocatechin  [4],  and  by  reduction  of  rufigallic  acid  [13].  Ali- 
zarin has  only  been  prepared  on  an  industrial  scale  from  anthra- 
quinone, and  the  artificial  product  has  practically  displaced  madder 
in  the  course  of  the  last  twenty  years. 

The  synthesis  of  alizarin  was  first  effected  by  Graebe  and 
Liebermann  in  1869.  These  chemists  had  already  observed  the 
formation  of  anthracene  from  natural  alizarin  by  heating  with 
zinc  powder,  and  recognizing  alizarin  as  a  derivative  of  anthra- 
cene, attempted  to  convert  anthracene  into  alizarin,  This  aim 
was  accomplished  by  fusion  of  bibromanthraquinone  with  potash. 
In  the  same  year  Graebe,  Liebermann,  and  Caro  [14]  discovered 
the  formation  of  alizarin  by  melting  anthraquinonesulphonic 

G2 


84  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

acid  with  caustic  potash.  This  process,  which  is  in  use  at  the 
present  day,  was  discovered  almost  simultaneously  by  W.  H. 
Perkin  [15]. 

Other  processes  have  been  proposed  for  the  manufacture  of 
alizarin,  for  instance  by  melting  dichloranthraquinone  or  nitro- 
anthraquinone  [16]  with  caustic  potash,  but  these  processes  have 
never  attained  commercial  importance. 

For  a  long  time  it  was  thought  that  the  anthraquinonedisul- 
phonic  acids  gave  rise  to  the  formation  of  alizarin,  but  this 
assumption  was  based  on  an  error.  The  monosulphonic  acid  alone 
is  capable  of  giving  alizarin,  while  the  disulphonic  acids  yield 
isopurpurin  and  flavopurpurin.  This  was  already  known  to  some 
technologists  in  1871,  but  was  first  published  by  Perkin  in  187(> 
[17]. 

The  formation  of  alizarin  from  anthraquinonesulphonic  acid 
does  not  appear  to  be  due  to  any  uniform  reaction.  On  the  one 
hand,  oxyanthraquinone  is  formed  and  becomes  oxidised  in  the 
alkaline  melt  to  alizarin;  on  the  other  hand,  oxyanthraqui- 
nonesulphonic  acid  is  also  a  constituent  of  the  melt,  and  yields 
alizarin  by  replacement  of  its  sulpho-group  by  hydroxyl.  Aliza- 
rinsulphonic  acids  are  also  often  found  in  the  alizarin  melt.  It 
is  not  improbable  that  these  different  reactions  are  due  to  the 
existence  of  several  isomeric  anthraquinonesulphonic  acids. 

For  the  manufacture  of  alizarin  on  a  large  scale  a  very  pure 
anthraquinone  is  required,  and  this  is  generally  prepared  by  oxi- 
dation of  anthracene  with  sodium  bichromate  and  dilute  sulphuric 
acid.  The  anthracene  is  generally  a  50-per-cent.  product  which 
has  oeen  converted  into  a  soft  powder  by  subliming  with  super- 
heated steam.  The  oxidation  takes  place  in  lead-lined  vessels  in 
which  the  mixture  is  heated  by  direct  steam.  By  employing  a 
pure  anthracene  and  a  not  too  concentrated  oxidation-mixture,  the 
anthraquinone  separates  as  soft  grey  powder,  which  is  freed  from 
acid  by  washing  with  water.  The  crude  product  is  then  dried, 
dissolved  in  concentrated  sulphuric  acid,  and  precipitated  with 
water.  A  further  purification  is  effected  by  sublimation  with 
superheated  steam. 

For  production  of  monosulphonic  acid  a  somewhat  concentrated 
fuming  sulphuric  acid  (containing  30  to  40  per  cent,  anhydride) 
is  required,  and  the  sulphonation  should  take  place  at  as  low  a 
temperature  as  possible. 


OXYQUINONES  AND  QUINONEOXIMES.  85 

The  monosulphonic  acid  is  separated  from  the  disulphonic  acids 
simultaneously  formed  by  fractional  crystallisation  of  the  sodium 
salts.  By  saturating  the  acid  mixture  with  soda,  the  salt  of  the 
monosulphonic  acid  separates  first.  At  present  the  sulphonation 
is  carried  out  so  as  to  produce  as  much  monosulphonic  acid  as 
possible  with  only  a  little  disulphonic  acid. 

As  has  already  been  stated,  the  reaction  in  the  melt  proceeds  in 
two  directions,  viz.,  a  substitution  of  the  sulpho-group  by  hydroxyl 
and  a  direct  oxidation. 

In  the  older  processes  this  oxidation  was  effected  by  air,  and  if 
the  supply  of  this  was  insufficient,  took  place  at  the  cost  of  some  of 
the  materials.  To  prevent  this  a  large  surface  of  the  melt  was 
exposed  to  the  air  by  melting  in  shallow  pans. 

This  process  has  been  abandoned  for  about  ten  years,  and  the 
atmospheric  oxygen  is  dispensed  with  by  adding  an  oxidising  agent 
(potassium  chlorate),  and  operating  in  closed  vessels  under  pres- 
sure. This  improvement  is  of  great  advantage,  as  the  temperature 
is  easily  regulated,  even  if  the  melt  contains  much  water;  while  in 
open  vessels  a  certain  concentration  is  necessary  before  the  required 
temperature  is  reached.  In  place  of  the  older  melting  process, 
the  sulphonic  acids  are  now  heated  with  concentrated  soda-lye 
under  pressure. 

The  operation  takes  place  in  a  horizontal  cylindrical  iron  vessel  ' 
fitted  with  a  stirrer.     Into  this  are  introduced  one  part  of  anthra- 
quinonemonosulphonate  of  soda,  with  about  three  parts  of  caustic 
soda  and  a  certain  amount  of  water  and  chlorate  of  potash.     The 
mixture  is  then  heated  several  days  to  180°-200°. 

The  melt  is  then  dissolved  in  water  and  the  sodium  compound 
decomposed  by  adding  hydrochloric  acid.  The  precipitate  of 
alizarin  is  then  well  washed,  and  brought  into  commerce  as  a 
10  to  20  per  cent,  paste.  Its  value  may  be  ascertained  by  an  esti- 
mation of  the  solid  matter  and  ash,  a  dye-trial  also  being  made. 

Blue  and  yellow  shades  of  alizarin  are  known ;  the  former  con- 
sists of  pretty  pure  alizarin,  while  the  latter  contain  both  the 
trioxyanthraquinones  isopurpurin  and  flavopurpurin.  Alizarin 
may  be  fixed  directly  on  wool,  the  shade  produced  being  weak,  and 
of  the  yellowish-red  tone  characteristic  of  free  alizarin  solutions. 
This  shade  has  no  value  in  dyeing,  and  the  application  of  alizarin 
is  solely  in  form  of  its  brightly  coloured  aluminium,  chromium,  and 
iron  lakes. 


86  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Most  of  the  alizarin  made  is  used  in  cotton-dyeing  and  printing,, 
although  a  considerable  amount  is  also  used  in  wool- dyeing. 

Alizarin  gives  entirely  different  shades  with  different  metals. 
In  dyeing  and  printing  the  beautiful  red  alumina  lake  and  the 
violet-black  iron  lake  are  almost  exclusively  used.  Sometimes  the 
chromium  lake  is  also  applied. 

In  order  to  dye  alizarin  on  cotton,  the  latter  is  impregnated 
with  the  necessary  metallic  oxide,  and  brought  into  a  bath  con- 
taining alizarin  in  a  fine  state  of  suspension,  the  bath  being  gra- 
dually heated  to  boiling;  although  alizarin  is  so  slightly  soluble 
in  water,  its  solubility  is  sufficient  to  effect  its  combination  with 
the  metallic  oxide  on  the  fibre.  For  test-dyeing  with  alizarins 
printed  calico  is  used.  This  calico  contains  stripes  of  alumina  and 
iron  and  mixtures  of  these,  printed  in  different  degrees  of  strength, 
and  on  dyeing  in  an  alizarin-bath  various  shades  are  obtained. 

In  printing,  a  mixture  of  alizarin  paste  and  aluminium  or  iron 
acetate  is  used.  On  steaming,  the  acetate  is  decomposed,  and  the 
formation  of  the  colour-lake  takes  place. 

In  alizarin-dyeing,  a  great  number  of  purely  empirical  opera- 
tions are  common,  especially  in  turkey-red  dyeing.  Brilliant 
scarlet  tones  of  turkey-red  can  only  be  obtained  on  alumina  and 
oil  mordants.  The  oil  formerly  used  was  a  very  rancid  olive-oil, 
"  Huile  tournante,"  but  this  has  been  entirely  replaced  by  the 
so-called  turkey-red  oil.  This  product  is  a  ricinoleate  of  ammonia, 
obtained  by  treating  castor-oil  with  strong  sulphuric  acid,  and 
neutralizing  the  separated  fatty  acid  with  ammonia.  It  is  probable 
that  the  alumina  forms  double  compounds  with  the  fatty  acids  and 
with  the  alizarin,  these  compounds  possessing  a  more  brilliant 
colour  than  the  simple  alizarin  lakes.  The  turkey-red  process  is 
very  complicated,  and  comprises  many  operations  which  are  not 
properly  understood.  For  instance,  treatment  in  a  bath  of  cow- 
dung  and  other  similar  processes. 

Wool  is  mordanted  with  alumina,  for  alizarin-dyeing,  generally 
by  boiling  in  a  bath  of  alum  tartar.  Chromium  mordants  are 
also  used  in  connection  with  alizarin  for  production  of  maroon 
shades. 

The  shades  obtained  with  alizarin  are  very  stable.  They  resist 
the  action  of  soap  and  bleaching-powder,  and  are  almost  entirely 
unaffected  by  light. 


OXYQUINONES  AND  QUINONEOXIMES.  87 

Nitroalizarin  [18,  19]. 
C14H7(N02)04. 

(1)        (2)         (3) 

Only  the  /3-nitro-compound  (of  the  constitution  OH  OH  NO2) 
possesses  technical  interest.  It  may  be  obtained  by  treating 
alizarin,  suspended  in  toluene  or  nitrobenzene,  with  nitrous  acid, 
or  by  cautious  nitration  of  alizarin  dissolved  in  glacial  acetic  acid 
with  nitric  acid. 

Pure  /3-nitroalizarin  forms  orange-yellow  needles,  which  melt 
at  244°,  with  partial  decomposition  [19] .  It  sublimes  in  yellow 
leaflets,  undergoing  partial  decomposition.  It  dissolves  in  benzene 
and  glacial  acetic  acid,  and  gives  a  purple-red  solution  with 
alkalies.  The  violet  lime-lake  is  not  decomposed  by  carbonic 
acid.  (Distinction  from  alizarin.)  It  forms  a  diacetyl  compound, 
M.P.  218°  [19].  Nitroalizarin  dyes  orange  shades  on  alumina 
mordants,  and  reddish- violet  on  iron  mordants. 

It  comes  into  commerce  in  paste  as  Alizarin  Orange,  and  is 
used  in  dyeing  and  printing,  though  its  principal  application  is  in 
the  manufacture  of  Alizarin  Blue. 


TRIOXYANTHRAQUINONES. 
CMH5(OH)302. 

A.  Purpurin  [position  i,  2, 4]. 

Purpnrin  occurs  with  alizarin  in  the  madder  root  [20],  pro- 
bably also  as  glucoside.  It  may  be  obtained  artificially  from 
alizarin  by  heating  with  manganese  dioxide  and  sulphuric  acid 
[21],  or  arsenic  acid;  and  also  by  melting  an  alizarinsulphonic 
acid  (the  so-called  alizarin  purpursulphonic  acid)  with  potash 

EH]. 

Purpurin  forms  long  orange-yellow  needles  which  contain  one 
molecule  of  water.  It  dissolves  pretty  readily  in  alcohol,  ether, 
and  benzene,  and  is  also  much  more  easily  soluble  in  water  than 
alizarin.  It  loses  its  water  of  crystallisation  at  100°,  and  sublimes 
at  a  comparatively  low  temperature.  M.P.  253°. 

The  alkaline  solutions  of  purpurin  are  reddish  violet,  and 
rapidly  become  bleached  on  exposure  to  light  and  air.  The 
presence  of  certain  metallic  oxides  produces  a  characteristic  effect 
on  the  absorption-spectrum  of  purpurin  solutions,  and  these  may 


V 


88  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

serve  for  the  detection  of  alumina  and  magnesia  [22,  23]  .  Pur- 
puriii  dissolves  in  boiling  alum  solution,  forming  a  yellowish-  red 
fluorescent  solution,  from  which  the  purpurin  separates  on  cooling. 
As  alizarin  is  almost  insoluble  in  alum  solution,  this  method  is 
used  for  the  separation  of  these  bodies.  Although  the  alkaline 
solutions  of  purpurin  are  easily  bleached  by  light,  the  alumina 
lake  is  perfectly  stable  against  this  agency. 

On  alumina  mordants  purpurin  produces  a  beautiful  scarlet 
red,  much  yellower  in  tone  than  that  from  alizarin,  but  its  appli- 
cation is  limited,  as  its  price  is  much  higher  than  that  of  iso- 
purpurin. 

B.  Isopurpurin  (Anthrapurpuriri)  [24,  25,  26]. 


Isopurpurin  is  obtained  by  melting  /3-anthraquinonedisulphonic 
acid  with  caustic  potash,  an  isomer  of  alizarin,  isoanthraflavic 
acid,  being  formed  as  a  bye-product  [26]  . 

In  the  first  stage  mono-oxyanthraquinonesulphonic  acids, 


are  formed,  and  these  are  oxidised  to  alizarins  ulphonic  acids,  a 
small  portion  being  converted  into  anthraflavic  acids.  These  aliza- 
rinsulphonic  acids  yield  the  purpurins  by  exchange  of  a  sulpho- 
f  or  an  hydroxyl  group  [42]  . 

It  forms  orange  needles,  which  are  soluble  in  alcohol  but  in- 
soluble in  benzene.  Its  M.P.  is  above  330°  [25].  It  yields  no 
phthalic  acid  on  oxidation,  and  therefore  probably  contains  the 
third  OH-group  in  the  second  benzene  ring.  Isopurpurin  is  the 
principal  constituent  of  the  commercial  alizarin  for  red.  It  dyes 
a  fine  scarlet  red  on  alumina  ;  its  iron  lake  is  greyish  violet,  and  of 
little  value. 

C.  Flavopurpurin  [26,  27]. 

OH  T41  C  H  I  M  CO  [mc  H   f  [6]  OH 

C6H3|[2]  CO  [2]  j  C(jH2t  [5]  OH' 

Flavopurpurin  is  obtained  from  a-anthraquinonedisulphonic 
acid  ;  anthraflavic  acid,  an  isomer  of  alizarin,  is  formed  as  a  bye- 


OXYQUINONES  AND  QUINONEOXIMES. 


89 


product.  It  forms  golden-yellow  needles,  easily  soluble  in  alcohol, 
M.P.  above  330°  C.  It  dissolves  with  purple-red  colour  in  caustic 
soda,  and  yellowish-red  in  ammonia  and  sodium  carbonate. 

On  alumina  mordants  it  gives  a  red,  which  is  still  yellower  than 
that  with  isopurpurin.  Its  principal  application  is  in  printing, 
while  that  of  isopurpurin  is  in  dyeing.  Anthraflavic  acid  and 
isoanthraflavic  acid  sometimes  occur  in  the  commercial  products. 
They  are  entirely  valueless  in  dyeing,  and  are  produced  in  badly 
conducted  operations. 

Like  isopurpurin,  flavopurpurin  contains  the  third  hydroxyl- 
group  in  the  second  benzene  nucleus. 

D.  Anthragallol  [41]. 

This  trioxyanthraquinone  is  not  prepared  from  anthracene,  but 
is  obtained  by  condensation  of  gallic  acid  with  benzoic  acid.  In 
anthragallol  the  three  hydroxyl- groups  occupy  adjacent  positions 
[1:  2:  3]. 

It  is  prepared  by  heating  equal  molecules  of  benzoic  acid  and 
gallic  acid  with  concentrated  sulphuric  acid.  The  following 
equation  expresses  the  reaction  which  takes  place  : — 

II  OH  CO          OH 


Anthragallol  has  a  brown  colour,  and  dyes  brown  shades  on 
alumina  or  chromic  oxide.  The  commercial  Alizarin  Brown  is  a 
mixture  of  anthragallol  with  more  or  less  rufigallic  acid. 

The  latter  compound  is  hexaoxyanthraquinone,  and  is  formed 
in  a  similar  manner  to  anthragallol  by  condensation  of  gallic  acid. 
It  belongs  to  the  mordant  anthraquinone- derivatives. 

Alizarin  Bordeaux  and  Alizarin  Cyanine  [38,  39]. 

On  treating  dry  alizarin  with  a  large  quantity  of  sulphuric  acid 
containing  70  per  cent,  anhydride,  a  peculiar  ether  of  sulphuric  acid 
is  obtained,  which  on  boiling  with  water  splits  up  into  a  uew 


3«4 


90 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


dyestuff,  "  Alizarin  Bordeaux,0  and  sulphuric  acid.     This  alizarin 
Bordeaux  is  a  tetraoxyanthraquinone  identical  with  quinalizarin  : 
Oil         CO         OH 


OH         CO 

This  dyestuff  produces  fine  Bordeaux  shades  on  alumina  mor- 
dants, and  in  colour-printing  a  blackish  blue  is  obtained  with  a 
chromium  mordant.  On  wool  a  deep  claret  with  a  violet  tone  may 
be  obtained.  Alizarin  Bordeaux  crystallises  from  nitrobenzene 
in  fine  red  needles  which  have  a  metallic  lustre.  It  may  be  dis- 
tilled, undergoing  only  slight  decomposition. 

If  alizarin  Bordeaux  be  dissolved  in  concentrated  sulphuric  acid 
and  treated  with  manganese  peroxide  or  arsenic  acid,  oxidation 
takes  place,  a  pentoxyanthraquinone  being  formed  : — 
OH          CO         OH 


OH         CO         OH 

This  body  comes  into  commerce  as  Alizarin  Cyanine  R  or  as 
Alizarin  Blue  CR.  Alizarin  cyanine  crystallises  from  glacial 
acetic  acid  in  beautiful  crystals,  and  dissolves  in  concentrated 
sulphuric  acid  with  a  blue  colour  and  a  fine  red  fluorescence.  If 
dyed  on  cotton  mordants  with  alumina,  fine  violet  shades  are 
produced,  and  chromium  mordants  give  dark  blues.  In  the  pre- 
paration of  alizarin  cyanine  R,  a  sulphuric  ether  is  formed  as 
intermediate  product,  and  on  treating  with  ammonia  this  body 
yields  a  dyestuff  which  differs  from  alizarin  cyanine  R  inasmuch  as 
it  produces  considerably  greener  shades.  It  is  also  a  commercial 
product,  and  is  sold  under  the  name  Alizarin  Cyanine  G. 
Analogous  series  of  reactions  may  be  carried  out  with  the  isomers 
and  homologues  of  alizarin,  for  example,  "  Bordeaux"  and  "  Cya- 
nines  "  corresponding  to  those  described  above  may  be  obtained 
from  purpurin,  anthrapurpurin,  flavopurpurin,  and  anthragallol. 


OXYQUINONES  AND  QUINONEOXIMES. 


Alizarin  Slue  [28,  29,  30]. 


91 


This  dyestuff  is  prepared  by  heating  /3-nitroalizarin  with 
glycerine  and  sulphuric  acid.  It  is  peculiar  in  so  far  that  it 
possesses  the  lake-forming  properties  characteristic  of  the  alizarin 
dyes,  and  is  at  the  same  time  a  weak  base.  Alizarin  blue  was 
discovered  by  Prud'homme  [28],  and  the  determination  of  its 
constitution  by  Graebe  [29]  led  to  the  synthesis  of  quinoline  by 
Skraup  from  glycerine,  nitrobenzene,  and  aniline. 

Alizarin  blue  has  the  composition  C17H9NO4,  and  stands  in 
the  same  relation  to  alizarin  as  quinoline  to  benzene. 

Its  constitutional  formula  is  as  follows  [29] : — 

CO          OH 


In  the  pure  state  (crystallised  from  benzene)  it  forms  brownish- 
violet  needles,  insoluble  in  water  and  difficultly  soluble  in  ether 
and  alcohol.  It  melts  at  270°,  and  sublimes,  forming  orange 
vapours.  It  dissolves  in  alkalies  with  a  blue  colour,  an  excess  of 
alkali  turning  the  solution  green.  Its  salts  with  acids  are  of  a 
reddish  colour,  and  are  decomposed  by  water. 

On  distillation  with  zinc  powder  it  yields  anthraquinoline, 
C1THUN  [29]. 

With  chromium  oxide,  alizarin  blue  gives  a  stable  indigo-blue 
lake. 

It  is  chiefly  applied  in  the  form  of  its  bisulphite  compound,  the 
latter  being  the  principal  constituent  of  the  commercial  Alizarin 
Blue  S  [3]].  This  is  a  reddish-brown  compound  and  is  decom- 
posed on  heating,  alizarin  blue  separating.  The  bisulphite  com- 
pound is  printed  with  acetate  of  chromium  ;  and,  on  steaming,  the 
chromium  lake  of  alizarin  blue  is  fixed  on  the  fibre.  The  bisul- 
phite compound  may  be  precipitated  from  its  solutions  by  common 
salt,  and  comes  into  commerce  as  an  easily  soluble  brown  powder. 


92  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Alizarin  Indigo-blue  S,  Alizarin  Green  S  [40]. 

Alizarine  blue  may  be  oxidised  by  action  of  fuming  sulphuric 
acid,  the  process  being  analogous  to  that  used  for  the  preparation 
of  Alizarin  Bordeaux.  At  50°  to  60°  a  dyestuff  called  Alizarin 
Blue-green  is  formed,  and  is  best  isolated  in  form  of  its  bisulphite 
compound.  It  is  a  monosul  phonic  acid  of  mono-oxyalizarin  blue. 

If  the  mixture  be  heated  to  120°,  or  if  alizarin  blue-green  is 
heated  with  concentrated  sulphuric  acid  to  120°,  an  intramolecular 
change  takes  place,  a  new  mono-oxyalizarin  blue  monosulphonic 
acid  being  formed.  This  body  is  an  article  of  commerce,  and  is 
known  as  Alizarin  Green  S. 

If,  finally,  the  temperature  of  the  reaction  between  sulphuric 
acid  and  alizarin  blue  be  raised  to  200°  to  210°,  or  if  alizarin 
green  is  heated  to  the  same  temperature  with  concentrated  sul- 
phuric acid,  a  third  dyestuff,  Alizarin  Indigo-blue,  is  obtained. 
This  body  is  a  trioxyalizarin-blue.  The  commercial  products  are 
pastes  which  contain  the  bisulphite  compounds.  The  shades  pro- 
duced in  dyeing  are  sufficiently  indicated  by  the  names,  being  a 
dull  indigo-blue  and  a  dull  bluish  green  respectively.  The  best 
results  are  obtained  with  chromium  mordants. 

Styrogallol  [36,  37]. 


This  compound  is  obtained  by  heating  gallic  acid  with  cinnamic 
acid  in  sulphuric  acid  solution  to  55°.  It  forms  light  yellow 
needles.  M.P.  350°.  It  is  insoluble  in  water,  and  sparingly 
soluble  in  alcohol,  glacial  acetic  acid,  and  aniline. 

Its  solution  in  alkalies  is  green,  changing  through  violet  to  red 
on  warming.  It  dissolves  in  strong  sulphuric  acid  with  a  yellowish- 
red  colour. 

Styrogallol  is  probably  an  o-dioxyanthracoumarine.  On  warming 
with  acetic  anhydride  a  diacetyl  derivative,  M.P.  260°,  is  obtained. 

On  alumina  mordants  it  dyes  an  orange-yellow  shade,  similar 
to  alizarin  orange,  but  owing  to  its  high  price  has  not  been  used 
practically. 

A  dibrominated  dioxy-/3-methylcoumarine  is  known  commer- 
cially as  Anthracene  Yellow. 


OXYQUINONES  AND  QUINONEOXIMES.  93 

QUINONEOXIMES. 

These  compounds  are  obtained  by  action  of  nitrous  acid  on 
phenols,  and  were  formerly  regarded  as  nitrosophenols ;  but  this 
assumption  has  gradually  been  abandoned.  They  may  also  be 
obtained  by  action  of  hydroxylamine  on  quinones,  and  yield 
dioximes  on  further  treatment  with  this  reagent.  It  is  therefore 
more  probable  that  the  nitrosophenols  are  really  oximes  of  quinones, 
i.  e.,  quinones  in  which  one  oxygen  atom  is  replaced  by  the  divalent 
group  =  N — OH. 

O  NOH 


O  O 

Quinone.  Quinoneoxime 

(Nitrosophenol). 

The  quinoneoximes,  like  the  quinones,  are  mostly  yellow,  but 
possess  little  tinctorial  power.  Certain  oxime-derivatives  of  ortho- 
quinones,  however,  like  oxy quinones,  are  capable  of  combining 
with  mordants  (especially  iron  and  cobalt),  forming  highly  coloured 
lakes  which  may  be  fixed  on  textile  fibres. 

Some  of  this  latter  class  of  quinoneoximes  are  described  in 
detail,  as  they  have  attained  some  importance  as  adjective  dye- 
stuifs. 

Dinitrosoresorcin  (Diquinoyldioxime)  [32]. 
C6H202(NOH)2. 

This  compound  is  obtained  by  treating  an  aqueous  solution  ot 
resorcin  with  nitrous  acid  (sodium  nitrite  and  sulphuric  acid). 
Dinitrosoresorcin  crystallises  from  alcohol  in  yellowish-brown 
leaflets,  which  deflagrate  at  115°.  It  is  a  pretty  strong  dibasic 
acid,  and  forms  easily  soluble  salts  with  alkalies. 

Its  constitution  is  probably  expressed  by  the  following  formula 
[33]  :_ 


CHEMISTRY  OF  ORGANIC  DYESTU1TS. 
O 


The  iron  lake  of  dinitrosoresorcin  is  green,  and  the  latter 
produces  green  shades  on  cotton  prepared  with  iron  mordants.  It 
has  been  used  for  some  time  in  cotton-dyeing  under  the  name 
"  Fast  Green." 


Naphthaquinoneoximes  [34]. 
C10H60(NOH). 

/3-naphthaquinone  yields  two  oximes,  both  of  which  are  capable 
of  dyeing  on  mordants,  while  this  property  is  absent  in  the  oxime 
of  a-naphthaquinone  (a-nitroso-a-naphthol), 

NOH 


a-nitroso-/3-naphthol  is  obtained  by  action  of  nitrous  acid  on 
/3-naphthol,  while  a-naphthol  under  similar  treatment  gives 
/3-nitroso-a-naphthol, 

0 


NOH 


along  with  some  a-a-compound. 

Both  derivatives  of  /3-naphthaquinone  give  intensely  green  lakes 
with  ferric  oxide,  while  their  cobalt  lake  is  dark  red,  being  known 


OXYQUINONES  AND  QUINONEOXIMES.  95 

in  commerce  as  Gambine  R  and  G  respectively ;  but  they  are  not 
of  great  importance. 

The  iron  salt  of  a  sulphonic  acid  of  the  a-/3-compound  comes 
into  commerce  as  Naphthol  Green  [38,  39]. 

The  sulphonic  acid  is  prepared  by  acting  on  Schaeffer's  acid 
with  nitrous  acid.  The  iron  compound  of  this  acid  is  soluble  in 
water,  and  is  fixed  on  animal  fibres  like  the  acid  dyestuffs. 

Naphthol  green  is  used  to  some  extent  in  wool-dyeing. 

The  dyestuff  known  as  Dioxine  is  a  nitroso-derivative  of  T8 
dioxynaphthalene. 


96  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


CHAPTER  IV. 

KETONEIHIDES  AND  HYDRAZIDES. 

THESE  bodies,  certain  of  which  have  been  used  as  dyes  tuffs,  are 
derived  from  the  simple  ketones  in  the  same  manner  as  the  quinone- 
imides  and  quinone-hydrazides  from  the  diketones  (quinones). 
Here,  however,  the  chromophor  occurs  in  an  open  carbon  chain, 
and  as  it  is  only  of  a  weak  character,  requires  a  salt-forming 
group  to  develop  the  properties  of  a  dyestuff.  The  colour  produced 
is  always  yellow. 

It  has  already  been  remarked  that  the  CO  group,  when  it  does 
not  occur  as  a  member  of  a  closed  carbon  ring,  cannot  act  as  a 
chromophor,  and  only  becomes  one  when  the  oxygen  is  replaced 
by  sulphur  or  by  a  nitrogenous  group.  So  far  as  the  present 
state  of  knowledge  reaches,  all  benzophenone  derivatives  are 
colourless.  On  the  other  hand,  thiobenzophenone  yields  coloured 
derivatives.  Tetramethyldiamidothiobenzophenone  [3]  :  — 


(CH3)2NC6H 

for  example,  is  intensely  yellowish  red,  but  is  no  dyestuff. 

If  the  sulphur  in  this  compound  be  replaced  by  the  imide-group 
NH,  auramine,  the  only  representative  of  the  ketoneimide  dye- 
stuffs  known,  is  formed. 

The  starting-point  for  the  manufacture  of  auramine  is  tetra- 
methyldiamidobenzophenone, 


(CH3)2NC6H/ 
This  base  was  discovered  by  Michler  [2]    in   1876,  and  has 


KETONEIMIDES  AND  HYDRAZIDES.  97 

recently  become  an  important  product  for  the  manufacture  of 
triphenylmethane  dyestuffs. 

Tetramethyldiamidobenzophenone  is  obtained  by  action  of 
carbon  oxychloride  or  of  perchlorformic  ether  on  dimethylaniline. 

The  analogous  thioketone  already  mentioned  is  obtained  in  a 
similar  manner  from  carbon  sulpho chloride,  CSC12?  and  dimethyl- 
aniline;  it  may  also  be  obtained  by  treating  the  corresponding 
oxygen  ketone  with  phosphorus  sulphide.  The  two  ketones  are 
similar  in  their  reactions  [3] . 

By  action  of  nascent  hydrogen,  tetramethyldiamidobenzophe- 
none  is  converted  into  the  corresponding  benzhydrol  [1] : — 

(CH3)2NC6H4xc/OH 
(CH3)2NC6H/  'XH 

This  compound  combines  with  acids  to  form  beautiful  blue 
salts,  which,  like  the  dyestuffs  of  the  rosaniline  series,  are  de- 
colorised by  excess  of  acid.  It  is  probable  that  in  these  coloured 
salts  the  compound  exists  as  an  anhydride,  as  is  the  case  with  the 
rosaniline  salts.  The  hydrochloride,  for  instance,  has  the  consti- 
tution : — 

(CH3)2N-C6H4 


(CH3)2N-C6H4 

ci71— 


/C-H. 


The  chloride  obtained  by  treating  tetramethyldiamidobenzo- 
phenone  with  a  phosphorus  chloride  is  probably  not  the  simple 
chloride 

(CH3)2N-C6H4 

6    4>C=C12; 
(CH3)2N-C6H/ 

but,  as  it  possesses  a  deep  blue  colour,  is  constituted  according  to 
the  formula  :  — 


-6^ 
(CH3)2N-C6H/°-CL 

ci71  -  1 


98  CHEMISTEY  OF  ORGANIC  DYESTUFFS. 

Auramine  [1,  4,  5,  7]. 

C17H21N3. 

This  dyestuff  was  discovered  simultaneously  by  A.  Kern  and 
H.  Caro,  and  is  formed  by  action  of  ammonia  on  tetramethyl- 
diamidobenzophenone.  It  is  best  prepared  by  melting  this  base 
with  ammonium  chloride  and  zinc  chloride.  The  reaction  is 
expressed  by  the  equation  :  — 

C17H20N20  +  NH3  =  C17H21N3  +  H2O  . 

Another  process  for  the  manufacture  of  auramine  consists  in 
allowing  ammonia  to  act  on  a  mixture  of  tetramethyldiamidodi- 
phenylmethane  or  tetramethyldiamidobenzhydrol  with  sulphur  at 
180°. 

Auramine  is  also  prepared  industrially  as  follows  :  — 
Dimethylamidobenzoic  chloride  is  produced  by  action  of  phos- 
gene on  dimethylaniline  ; 

+  COC12=C6H4-N(CH3) 


CO  01 

This  chloride  is  treated  with  diphenylamine,  whereby  dimethyl- 
amidobenzodiphenylamine  is  formed  ; 

C6H4-N(CH3)2 
CO-N(C6H5)2  ' 

Practically,  the  above  reactions  are  combined  into  one  operation. 
The  above  condensation-product  is  treated  with  a  chloride  of 
phosphorus  or  phosgene,  and  the  resulting  chloride, 

C6H4-N(CH3)2 

C-C12.N(C6H5)2' 
condensed  with  dimethylaniline,  and  the  compound  produced 

C6H4.N(CH3)2 


XC6H4.N(CH3)2.C1 


heated  with  ammonia  yields  auramiiie  and  diphenylamine. 


KETONEIMIDES  AND  HYDRAZIDES.  99 

Auramine  comes  into  commerce  as  the  hydrochloride  C17H21N3, 
HC1.  This  salt  is  easily  soluble  in  water,  and  crystallises  from 
this  medium  in  beautiful  golden-yellow  leaflets. 

It  is  decomposed  by  continued  boiling  with,  water,  especially 
in  presence  of  free  hydrochloric  acid,  tetramethyldiamidobenzo- 
phenone  and  ammonia  being  regenerated. 

Platinum  double  salt,  (C17H2iH3,HCl)2,PtCl4,  forms  an  orange- 
red  precipitate. 

Picrate,  C17H2iN3,C6H2(NO2)3OH,  forms  yellow  leaflets  sparingly 
soluble. 

Oxalate,  (C17H21N3)2C2H2O4,  forms  yellow  needles  sparingly 
soluble  in  water. 

Leuco-auramine  [7],  C17H23N3,  is  formed  by  reduction  of  an 
alcoholic  solution  of  auramine  with  sodium  amalgam.  It  forms 
colourless  crystals,  M.P.  135°,  and  dissolves  in  glacial  acetic  acid 
with  a  blue  colour  (see  under)  . 

Phenylauramine  and  tolylauramine  are  obtained  by  action  of 
aniline  and  toluidine  on  auramine  or  on  tetramethyldiamido- 
benzophenone. 

Auramine  must  be  regarded  as  the  imide  of  tetramethyldiamido- 
benzophenone,  and  accordingly  has  the  constitutional  formula  :  — 

(CH3)2N—  C6H4X 

>C=NH. 

(CH3)2N-C6H4 

The  ring  constitution  accepted  for  tetramethyldiamidobenz- 
hydrol  cannot  be  present  in  auramine,  as  the  elements  of  consti- 
tutional water  necessary  are  not  present.  The  yellow  colour  of 
auramine  also  is  against  the  assumption  of  a  ring  formula,  the 
benzhydrols  being  blue. 

On  the  other  hand,  a  ring-formation  is  probably  present  in  the 
blue  salt  formed  by  leucoauramine  and  acetic  acid,  and  this  Graebe 
expresses  by  the  formula  :;  — 


XC6H4N=  (CH,),' 


An   objection  to   this    formula    is    that   till   now   pentatomic 
nitrogen  is  only  known  in  combination  with  an  acid  radical  or 

H2 


100  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

hydroxyl.  Auramine  and  its  derivatives  are  the  only  dyestuffs 
known  which  belong  to  the  class  of  simple  ketoneimides.  The 
chromophor,  C=NH,  unlike  that  in  rosaniline  dyestuffs,  occurs 
in  an  open  chain,  and  in  this  respect  the  hydrazides  (Tartrazine) 
are  similar,  and  also  have  a  yellow  colour.  Auramine  is  one  of 
the  few  basic  yellow  dyestuffs,  and  owing  to  its  easy  fixation  on 
tannin  mordants  has  obtained  a  considerable  importance  in  cotton- 
dyeing  and  printing.  It  produces  a  pure  yellow  shade. 

Its    substitution-derivatives,    such    as    phenylauramine,    have 
mostlv  a  brown  colour,  and  have  not  been  applied  practically. 


PHENYLHTDKAZIDES  [8]. 

Phenylhydrazine  reacts  readily  with  most  compounds  which 
contain  the  group  CO  ;  the  oxygen  atom  being  eliminated  in  the 
form  of  water  with  two  hydrogen  atoms  of  the  phenylhydrazine, 
the  rest  of  the  latter  entering  in  the  place  of  the  oxygen. 

It  is  probable  that  the  two  hydrogen  atoms  which  split  off 
belong  to  the  amido-group,  and  therefore  the  hydrazides  contain 
the  group  C=  N— NHC6H5. 

That  a  close  relationship  exists  between  azo-compounds  and 
hydrazides  is  seen  from  the  fact  that  certain  oxyazo-compounds 
obtained  from  diazo-compounds  and  phenols  are  identical  with  the 
hydrazides  of  certain  quinones.  Indeed  all  coloured  hydrazides 
show  a  great  similarity  to  the  azo-compounds,  and  probably 
belong  to  this  class.  Both  classes  of  compounds,  for  example, 
behave  similarly  on  reduction.  The  hydrazine  group,  like  the 
azo-group,  is  split,  yielding  two  amido-groups,  one  of  which 
remains  in  combination  with  the  phenyl  group,  the  other  with 
the  carbon  atom. 

All  the  hydrazides  known  at  present  have  a  yellow  or  orange 
colour,  like  the  simpler  azo-compounds. 

Tartrazine. 

This  dyestuff  is  manufactured  by  action  of  phenylhydrazine- 
sulphonic  acid  on  dioxy-tartaric  acid.  This  acid,  which  in  the 
hydrated  condition  has  a  formula 


KETONEIMIDES  AND  HYDRAZIDES.  101 

COOH 
i/OH 

V\OH 

'/OH 

Son 

COOH, 

must  be  regarded  as  the  hydrate  of  a  diketonic  acid : 

COOH 

CO 
CO 


COOH. 


It  reacts  according  to  the  latter  formula  with  hydrazines,  two 
molecules  of  which  enter  into  reaction. 

The  product  obtained  with  two  molecules  of  phenylhydrazine 
has  a  beautiful  yellow  colour;  it  is  too  sparingly  soluble  to  be 
of  use  in  dyeing,,  but  a  valuble  dyestuff  may  be  obtained  by  intro- 
duction of  sulpho-groups. 

The  commercial  product  known  as  Tartrazine  is  a  sulphonic  acid 
prepared  by  the  action  of  two  molecules  of  phenylhydrazine- 
sulphonic  acid  (from  sulphanilic  acid)  on  one  molecule  of  sodium 
dioxytartrate  in  hydrochloric  acid  solution.  The  constitution  of 
tartrazine  is  probably  expressed  by  the  following  formula : — 

COOH 

C  =  N-NHC6H.S03H 

C=N-NHC6H4SO3H 


COOH. 


The  sodium  salt  of  tartrazine  forms  a  fine  orange-yellow 
crystalline  powder.  It  dyes  animal  fibres  from  an  acid  bath, 
producing  a  beautiful  gold-yellow  shade,  which  is  valuable  for 
its  stability  against  light  and  milling. 

The  application  of  higher  hydrazines  gives  rise  to  dyestuffs  of 
a  redder  tone. 


102  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


CHAPTER  V. 


TRIPHENYLMETHANE  DYESTUFFS. 

TRIPHENYLMETHANE  and  its  analogues  are  mother  substances 
of  a  series  of  dyestuffs,  many  of  which  are  of  great  technical 
importance. 

If  amido-  or  hydroxyl- groups  are  introduced  into  triphenyl- 
methane,  in  certain  positions,  colourless  compounds,  the  leuco- 
derivatives  of  dyestuffs,  are  formed. 

For  example,  if  three  amido-groups  are  introduced  into  the 
three  benzene  nuclei,  in  the  para  position  to  the  methane-carbon 
atom,  the  compound  known  as  paraleucaniline  is  formed, 

H2NC6H4v 

4>C— C6H4NH2. 
H2NC6H/  | 

H 

On  oxidation  this  compound  loses  two  hydrogen  atoms,  and  a 
condensation  takes  place  between  the  nitrogen  of  an  amido-group 
and  the  methane-carbon  atom,  pararosaniline  being  formed.  [See 
Introduction.] 

H2NC6H4v 

^C— C6H4. 
H2NC6H/  ' 

NH 

Pararosaniline  only  exists  in  the  form  of  its  salts,  and  in  the/ 
free  state  takes  up  one  molecule  of  water,  triamidotriphenyl-> 
carbinol,  a  colourless  compound,  being  formed, 

H2NC6H4 
4 
H2NC6H| 

OH 


TRIPHENYLMETHANE  DYESTUFFS. 


103 


This  transformation  into  colourless  carbinol-derivatives  takes 
place  with  all  basic  triphenylraethane  dyestuffs,  and  the  carbinols 
are  for  this  reason  regarded  as  the  bases  of  the  dyestuffs,  although 
this  assumption  is  not  altogether  correct.  Really  both  classes  of 
compounds  have  totally  different  constitutions,  as  in  the  dyestnffs 
a  closed  ring  is  present,  while  in  the  carbinols  it  is  absent.  In 
the  triphenylmethane  dyestuffs  the  chromophor  EEC — NH —  or 
=C — O —  is  always  present,  and  generally  effects  the  linkage 
between  several  aromatic  nuclei.  In  most  cases  it  occurs,  how- 
ever, in  one  ring,  occupying  two  para  positions.  For  instance, 
pararosaniline  contains  the  group : 


NH 


N— II 


C— 


which  shows  a  certain  analogy  to  quinones. 

The  imido-group  present  in  the  chromophor  also  serves  as  salt- 
forming  group,  and  appears  to  effect  a  combination  of  the  dye- 
£tflff  with  the  fibre.  For  instance,  animal  fibres  may  be  dyed  with 
the\  colourless  carbinol  bases,  just  as  with  the  dyestuffs  them- 
selves. Apparently  a  salt  is  formed,  in  which  the  fibre  acts  as  an 
acid,  and  combines  with  the  imido-group. 

The  basic  properties  of  the  amido-groups  present  only  be- 
come apparent  under  the  influence  of  strong  acids,  or  of  the 
haloid  derivatives  of  the  alcohol  radicals.  These  amido-groups, 
however,  intensify  the  basicity  of  the  imido-group.  The  forma- 
tion of  salts  with  these  groups  is  generally  attended  by  a  striking 
alteration  of  the  dyestuff  character. 

Basic  triphenylmethane  dyestuffs  mostly  form  sulphonic  acids  ; 
these  are  generally  acid  dyestuffs,  and  when  observed  in  the  free 
state  or  in  form  of  their  acid  salts  have  the  same  colour  as  the 


104  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

original  dyestuffs.  Their  neutral  alkali  salts  are  colourless,  and 
appear  to  be  carbinol  compounds. 

The  conversion  of  basic  carbinols  into  dyestuffs  is  generally 
gradual,  and  in  many  cases  the  formation  of  colourless  salts  of  the 
former  may  be  observed.  Tetramethyldiamidotriphenylcarbinol 
(the  base  of  malachite  green)  gives  a  colourless  solution  with 
dilute  acetic  acid,  the  formation  of  dyestuff  only  taking  place  on 
warming  or  after  long  standing. 

Numerous  methods  are  employed  for  the  production  of  tri- 
phenylmethane  dyestuffs. 

Substituted  benzophenones  may  be  condensed  with  tertiary 
bases  in  presence  of  a  dehydrating  agent. 


(CH3)2NC6H 

/V^V^  ~T  V^gJLJ.5.1^  I  V>iJ.o)o' 

(CH3)2NC6H/ 


;CO  +  C6H5N(CH 
Tetramethyldiamidobenzophenone.  Dimethylaniline. 

(CH3)2NC6H4 


/C~C6H4N(CH3)2 

(CH3)2NC0H/ 

Cl 

Hexamethylrosamline. 

The  chloride  of  tetramethyldiamidobenzophenone  reacts  in  a 
similar  manner.  This  compound  has  a  blue  colour,  and  probably 
belongs  to  the  diphenylmethane  dyestuffs,  which  are  analogous  to 
the  ros anilines.  It  has  the  constitution  : — 


Benzhydrol  obtained  by  reduction  of  tetramethyldiamidobenzo- 
phenone (compare  page  94),  and  which  also  in  form  of  its  salts 
behaves  like  a  dyestuff,  reacts  with  amines  with  the  greatest  ease. 

In  this  reaction  the  leuco-derivatives  of  the  dyestuffs  are 
obtained. 


TRIPHENYLMETHANE  DYESTUFFS.  105 

(CH3)2N  .  C6H4v 
(CH3)2N .  C6H/ 

Tetramethyldiamidobenzhydrol.         Dimethylaniline. 


H)C-CeH4N(CH3) 
.  C6H4'  i 
H 

Hexamethylparaleucaniline. 

Colouring-matters  (rosaniline,  methyl  violet)  of  this  class  are  also 
formed  by  oxidation  of  primary,  secondary,  or  tertiary  amines, 
which  contain  methyl  groups  in  combination  with  nitrogen  or 
carbon.  Further,  benzene-derivatives,  which  contain  no  methyl 
groups,  yield  dyestuffs  if  treated  with  compounds  which  at  the  same 
time  are  capable  of  withdrawing  hydrogen  and  supplying  carbon, 
such  as  carbon  tetrachloride,  oxalic  acid,  iodoform  (rosolic  acid, 
diphenylamine  blue).  Another  method  consists  in  the  direct 
introduction  of  amido-groups  into  triphenylmethane.  Again, 
aromatic  bases  or  phenols  yield  triphenylmethane-derivatives  by 
condensation  with  toluenes,  chlorinated  in  the  side  chain,  or  with 
aromatic  aldehydes.  In  most  of  these  cases  leuco- compounds  are 
obtained,  and  are  converted  into  dyestuffs  by  oxidation.  The 
phthalei'ns,  a  peculiar  class  of  triphenylmethane  dyestuffs,  are  pre- 
pared by  condensation  of  phthalic  anhydride  with  phenols. 

A.    ROSANILINE  DYESTUFFS. 

In  the  wider  sense  of  the  term,  this  class  comprises  all  the  basic 
dyestuffs  obtained  from  triphenylmethane  and  its  homologues. 
As  has  already  been  remarked,  the  salts  are  the  real  dyestuffs, 
while  the  so-called  colour-bases  are  colourless  carbinol  derivatives. 
Up  to  the  present,  no  suitable  nomenclature  has  been  applied  to 
the  actual  dyestuffs,  rosaniline  for  example  being  generally  called 
triamidotriphenylcarbinol,  and  this  method  has  been  adopted  in 
the  present  work;  although  in  reality  the  carbinol  bases  have 
little  or  nothing  to  do  with  the  dyestuffs,  so  far  as  constitution  is 
concerned. 

The  simpler  basic  triphenylmethane  dyestuffs  are  derivatives  of 


106  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

diamidotriphenylmethane.  This  compound  gives  a  violet  dyestuff 
on  oxidation,  which  has  not  been  submitted  to  a  close  investiga- 
tion [2] .  It  is  probably  a  member  of  the  class  of  compounds  in 
question,  and  has  the  constitution  : 


P  TJ       n/ 

C°H5~  "NCANH 


The  tetramethyl  derivative  of  the  above  compound  comes  next 
in  the  series,  and  is  a  well- character]' zed  substance. 


Tetrametliyldiamidotriplienylcarbmol  [3,  4,  5]. 

C6H4N(CH3)2' 
OH 

The  base,  separated  from  its  salts  by  alkalies,  forms  a  colourless 
or  slightly  grey  powder.  It  crystallises  from  ligroin  in  shining 
colourless  leaflets,  or  in  round  aggregates  of  crystals,  M.P.  120°. 
With  acids  the  compound  forms  intensely  green  salts,  water 
being  split  off.  As  the  amido-groups  contain  no  replaceable 
hydrogen,  and  as  it  is  scarcely  probable  that  the  hydrogen  neces- 
sary for  the  formation  of  water  is  withdrawn  from  the  methyl 
group,  it  may  be  accepted  that  the  hydrogen  atom  is  displaced  from 
a  molecule  of  the  acid,  and  that  the  salt  formed  has  a  similar  con- 
stitution to  the  salts  of  quaternary  ammonium  bases.  Accord- 
ingly the  hydrochloride  has  the  constitutional  formula  [3]  : 


XC6H4N(CH3)2* 

~ 


With  a  large  excess  of  acid,  the  pale  yellow  diacid  salt  may  be 
obtained.  The  monoacid  salts  are  characterized  by  the  ease  with 
which  they  crystallise  ;  they  are  beautiful  green  dyestuffs  of  great 
tinctorial  power  [5]  . 


TRIPHENYLMETHANE  DYESTUFFS.  107 

Hydrochloride,  C23H24N2,HC1,  forms  easily  soluble  green  leaflets. 

Sulphate,  C23H24N2,H2SO4,  crystallises  with  one  molecule  of 
H2O  in  brilliant  green  needles,  or  anhydrous  in  thick  green 
prisms. 

Zinc  chloride  double  salt,  (C23H24N2,C1)  8  +  2ZnCl2  +  2H2O,  forms 
brilliant  green  needles  or  leaflets. 

Oxalate,  2C23H24N2  +  3C2H2O4,  large  green  prisms,  easily  soluble 
in  water. 

Picrate  sparingly  soluble,  crystallises  in  golden-yellow  needles. 

Ethyl  ether, 

C6H5C=[C6H4N(CH3)2]2, 

OC2H5 

is    obtained   by   heating   the   base   with   alcohol   to   110°;    it  is 
colourless,  and  melts  at  162°. 
The  methyl  iodide  [5], 

C23H25(OCH3)N2,2CH3I  +  H2O, 

is  formed  by  heating  the  base  with  methyl  iodide  and  methyl 
alcohol.  It  forms  colourless  needles. 

Tetramethyldiamidotriphenylcarbinol,  or  more  correctly  its 
anhydride,  is  formed  by  oxidation  of  tetramethyldiamidotriphenyl- 
methane  [3],  and  by  condensation  of  two  molecules  dimethyl- 
aniline  with  one  molecule  benzotrichloride  in  presence  of  zinc 
chloride  [4],  It  may  also  be  obtained  from  benzoyl  chloride 
and  dimethylaniline  [3]  by  action  of  the  air. 

The  most  recent  method  of  preparation  is  by  action  of  dimethyl- 
aniline  on  the  chloride  obtained  by  treating  dimethylamido- 
benzophenone  with  phosphorus  trichloride. 

XC6H4N(CH3)2 


The  salts  of  tetramethyldiamidotriphenylcarbinol  come  into 
commerce  under  numerous  names,  of  which  Malachite  Green  and 
Benzaldehyde  Green  are  most  usual.  Malachite  green  has  at- 
tained considerable  importance ;  it  has  almost  treble  the  tinctorial 
power  of  the  older  methyl  green,  and  possesses  further  the 


108  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

advantages  of  dyeing  wool  easily  and  resisting  the  action  of  heat. 
The  oxalate  and  the  zinc-chloride  double  salt  are  most  frequently 
met  with. 

Malachite  green  was  first  prepared  by  E.  and  O.  Fischer  [3] 
by  oxidation  of  tetramethyldiamidotriphenylmethane.  Shortly 
afterwards  Doebner  obtained  it  by  action  of  benzotrichloride  on 
dimethylaniline,  a  process  which  was  patented  [4,  6]  and  used 
for  the  manufacture  of  the  dyestuff.  At  that  time  Fischer's 
method  of  preparation  was  not  practicable,  as  the  necessary  benz- 
aldehyde  could  not  be  obtained.  However,  the  difficulties 
encountered  in  the  technical  production  of  the  latter  were  soon 
overcome,  and  now  the  benzotrichloride  process,  which  gives  very 
unsatisfactory  results,  has  been  entirely  abandoned.  At  present 
the  manufacture  of  malachite  green  is  carried  out  as  follows  : — 

The  leuco-base  is  prepared  by  heating  one  molecule  of  benzalde- 
hyde  with  two  molecules  of  dimethylaniline  in  presence  of  hydro- 
chloric acid.  (Zinc  chloride  was  formerly  used,  but  has  been 
found  to  be  unnecessary.)  The  base  is  then  dissolved  in  the 
theoretical  quantity  of  hydrochloric  acid  and  the  calculated 
amount  of  finely  suspended  lead  peroxide  added  to  the  solution, 
which  must  be  very  dilute.  The  lead  is  removed  as  sulphate  by 
adding  sodium  sulphate,  and  the  dyestuff  precipitated  by  adding 
zinc  chloride  and  salt. 


Nitro-derivatives  of  Tetrametliyldiamidotriphenylcarlinol 

[3,  8]. 

The  paranitro-compound  is  obtained  by  oxidation  of  nitro- 
tetramethyldiamidotriphenylmethane  (from  paranitrobenzalde- 
hyde  and  dimethylaniline)  and  also  by  action  of  paranitro- 
benzoyl-chloride  and  atmospheric  oxygen  on  dimethylaniline  [3] . 

The  base,  C23H25N2O (NO2) ,  crystallises  in  yellow  prisms.  The 
salts  are  green,  and  are  decomposed  by  water.  On  partial 
reduction  a  violet  dyestuff  (probably  tetramethylpararosaniline) 
is  formed ;  complete  reduction  yields  tetramethylparaleucaniline. 

The  meta-compound  [2,  8]  is  formed  by  oxidation  of  the  nitro- 
tetramethyldiamidotriphenylmethane  obtained  from  metanitro- 
benzaldehyde  and  dimethylaniline.  It  is  similar  to  the  former 
compound,  but  does  not  yield  a  violet  dyestuff  on  reduction. 


TRIPHENYLMETHANE  DYESTUFFS.  109 

DichlortetrametkyldiamidotripJienylcarUnol  [11]. 
C23H24N2C12O. 

The  salts  of  this  compound  come  into  commerce  as  Victoria 
Green  3  B  or  New  solid  Green  3  B.  It  is  prepared  by  condensa- 
tion of  dichlorbenzaldehyde  with  dimethylaniline  and  subsequent 
oxidation  of  the  leuco-base  formed.  Its  shade  is  bluer  than  that 
of  malachite  green. 

TetraethyldiainidotriplienylcarMnol  [7] . 
C27H32N2O. 

The  salts  of  this  base  come  into  commerce  under  the  names 
Brilliant  Green,  New  Victoria  Green,  Ethyl  Green,  and  Solid 
Green.  The  sulphate,  C27H32N2,H2SO4,  is  most  commonly  met 
with.  It  forms  brilliant,  gold  shimmering  needles.  The  zinc- 
chloride  double  salt  forms  brilliant  green  needles.  In  dyeing 
brilliant  green  produces  yellower  shades  than  malachite  green. 

Sulphonic  Acids  [9,  10]. 

These  bodies  are  in  considerable  demand,  especially  for  wool- 
dyeing,  and  numerous  products  are  met  with  in  commerce.  They 
are  generally  prepared  by  sulphonation  of  the  leuco-bases,  and 
subsequent  oxidation ;  as  the  bases  themselves  do  not  give  good 
results  on  direct  sulphonation.  The  sulpho-group  enters  especi- 
ally easily  into  benzylated  bases ;  and  probably  enters  the  benzene 
ring  of  the  benzyl  group. 


Helvetia  Green. 
C23H25N204SNa. 

This  dyestuff,  which  is  obtained  by  sulphonation  of  leuco- 
malachite  green,  and  subsequent  oxidation,  is  the  oldest  of  its 
class ;  but  is  not  much  used  at  present,  as  its  acid  properties  are 
only  slightly  developed. 


110  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


Light  Green  S. 

C37H35N2010S3Na. 

This  dyestuff  is  known  also  as  Acid  Green,  Light  Green  S  F, 
and  Guinea-Green  B,  and  is  the  most  important  of  this  class.  The 
leuco-base  used  for  its  production  is  diethyldibenzyldiamido- 
triphenylmethane,  obtained  by  condensation  of  ethylbenzyl- 
aniline  and  benzaldehyde.  The  resulting  body  is  sulphonated 
and  oxidised.  Light  Green  S  F  dyes  wool  and  silk  from  an  acid 
bath  (Friedlander,  B.B.  1889,  p.  588). 

Certain  blue  dyestuffs  which  belong  to  this  class  have  recently 
been  introduced  into  the  market.  They  are  prepared  by  conden- 
sation of  dimethylaniline,  diethylaniline,  and  ethylbenzylaniline 
with  metaoxy-  or  meta-amidobenzaldehyde.  The  resulting  leuco- 
bases  have  the  formulae  : — 

/C.H4OH(m)  /CcH4OH(m) 

HC  or   HC 

\\[C6H4N(CH3)J2  \ 

The  commercial  dyestuffs  known  as  Patent  Blue  N  and  Super- 
fine are  lime-salts  of  the  sulphonic  acids,  obtained  by  sulphonation 
and  subsequent  oxidation  of  the  above  leuco-bases.  The  shades 
produced  are  similar  to  those  of  indigo  extract,  and  have  the 
advantage  of  greater  fastness  and  brilliancy  (D.  R.  P.  46384, 
48523;  Chemikerz.  1889,  p.  1702). 

A  further  dyestuff  derivative  of  diamidotriphenylmethane  is 
Quinoline  Green  [1],  obtained  by  action  of  tetramethyldiamido- 
benzophenone,  its  chloride,  or  its  hydrol  on  quinoline.  In  the  last 
case  a  leuco-compound  is  formed. 

The  dyestuff  is  probably  constituted  according  to  the 
formula : — 

(CH3)2=NC6H 

(CH3)2=NC6H/| 

Cl 

Acid  Violet  Nis  a  dyestuff  of  similar  properties,  and  probably  of 
similar  constitution  to  the  above. 


TRIPHENYLMETHANE  DYESTUFFS.  Ill 


Triamido tripheriylcarbinol,  Pararosaniline. 


H2NCUH4-CX 


/C6H4NH2 
C6H4NH2' 


The  anhydride  occurs  only  in  the  coloured  salts  ;  for  example, 
in  the  hydrochloride  :  — 

/CCH4NH2 
HN-^CH—  C 

CH4NHHC1 


The  amido-groups  of  pararosaniline  are  in  the  para  position  to 
the  methane- carbon  atom.  It  is  formed  by  heating  two  molecules 
of  aniline  and  one  molecule  of  paratoluidine  [11]  with  arsenic 
acid,  mercuric  chloride,  or  other  oxidizing  agents ;  by  partial 
reduction  of  trinitrotriphenylcarbinol  with  zinc  powder  and 
acetic  acid  [12]  ;  by  oxidation  of  triamidotriphenylmethane 
(paraleucaniline)  [12]  ;  by  heating  aurine  with  ammonia  to  120° 
[12] ;  and  by  heating  pure  aniline  with  carbon  tetrachloride, 
ethylene  chloride,  or  iodoform.  It  may  also  be  obtained  by 
action  of  paranitrobenzaldehyde  [14],  paranitrobenzyl-  and  benzoyl 
chloride  [15],  or  paranitrobenzyl- alcohol  on  aniline. 

The  base  forms  colourless  leaflets  sparingly  soluble  in  cold,  more 
easily  in  hot  water.  It  combines  with  one  molecule  of  acid  ta 
form  salts  of  an  intense  red  colour.  With  an  excess  of  acid, 
yellow  triacid  salts  are  formed,  which  are  decomposed  by  water. 

On  reduction,  pararosaniline  yields  paraleucaniline  (triamido- 
triphenylmethane) . 

By  heating  with  hydriodic  acid  in  a  sealed  tube  it  splits  up 
into  aniline  and  paratoluidine.  Pararosaniline  was  discovered  by 
Rosenstiehl  [16],  and  its  constitution  determined  by  E.  and  O. 
Fischer  [12].  The  above  constitutional  formula  is  deduced  from 
the  following  facts  : — 

On  treating  with  nitrous  acid,  pararosaniline  gives  a  hexazo- 
compound,  i^  which  all  three  nitrogen  groups  are  present  as  diazo- 
groups  (probably  carbinol  compound) .  On  boiling  with  alcohol 
this  diazo-compound  yields  triphenylmethane,  C19H16. 


112  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

On  partial  reduction  trinitrotriphenylcarbinol  yields  pararos- 
aniline  [12];  paraleucaniline  being  formed  on  further  reduction. 

By  action  of  paranitrobenz aldehyde  on  aniline  in  presence  of 
zinc  chloride,  nitrodiamidodiphenylmethane  is  formed;  yielding 
paraleucaniline  on  reduction  [12] . 

Pararosaniline  is  present  in  most  commercial  rosanilines.  Its 
salts  are  similar  to  those  of  the  latter,  but  are  in  general  somewhat 
more  easily  soluble  in  water. 

The  synthesis  of  pararosaniline  (from  paranitrobenzaldehyde, 
&c.)  [14,  15,  17,  18]  has  until  now  not  been  carried  out  on  a 
large  scale,  but  it  may  be  expected  that  in  course  of  time  the 
technical  difficulties  which  stand  in  the  way  of  these  processes 
will  be  overcome.  Recently  pararosaniline  has  been  manufactured 
by  a  synthetic  process  based  on  the  following  lines.  Anhydroform- 
uldehydeaniline,  obtained  by  action  of  formaldehyde  on  aniline, 
is  heated  with  aniline  and  aniline  hydrochloride,  whereby  diamido- 
diphenylmethane  is  formed.  This  latter  compound,  on  heating 
Avith  aniline,  aniline  hydrochloride,  and  an  oxidising  agent  yields 
pararosaniline. 


Methyl  Violet  [19]. 

The  commercial  products  known  under  this  name  are  prepared 
l)y  oxidation  of  dimethylaniline  sometimes  containing  monome- 
thylaniline.  The  dimethylaniline  is  mixed  with  sulphate  or  chlo- 
ride of  copper,  acetic  acid,  potassium  chlorate,  and  a  large  quantity 
of  common  salt.  A  more  recent  process  consists  in  using  phenol 
in  place  of  acetic  acid — the  chlorate  being  generally  dispensed 
with.  During  the  actual  process  the  cupric  chloride  becomes  re- 
duced to  cuprous  chloride,  which  oxidises  again  at  the  expense  of 
the  chlorate  or  by  the  atmospheric  oxygen,  thus  acting  as  oxygen- 
carrier.  Cuprous  chloride  is  capable  of  forming  an  almost  in- 
soluble double  chloride  with  methyl  violet,  this  property  being 
absent  in  cupric  chloride.  Formerly  the  double  compound  was 
decomposed  by  sulphuretted  hydrogen,  the  soluble  violet  being 
separated  from  copper  sulphide  by  nitration.  At  present  the 
same  end  is  attained  by  addition  of  ferric  chloride,  w).jich  oxidises 
the  cuprous  salt  to  cupric  chloride,  which  remains  in  the  mother- 
liquor  after  the  violet  has  been  salted  out. 


TRIPHENYLMETHANE  DYESTUFFS.  113 

The  following  will  give  an  idea  how  the  phenol  process  is  carried 
out  on  a  large  scale.  The  operation  takes  place  in  a  drum,  which 
is  jacketed,  and  connected  with  steam-  and  cold-water  supplies. 
Finely  powdered  salt  and  copper  sulphate  are  stirred  with  phenol 
and  a  little  water  to  a  homogeneous  mixture.  Dimethylaniline  is 
then  added,  and  the  whole  heated  to  55°,  with  continual  stirring, 
care  being  taken  that  the  temperature  does  not  rise  above  60°. 
After  a  few  hours  the  cover  is  removed,  to  allow  the  air  to  act, 
the  temperature  being  maintained  at  55°.  The  process  is  ended 
in  about  8  hours,  and  the  melt  is  cooled  by  passing  cold  water 
into  the  casing  of  the  drum.  The  melt  is  dissolved  in  water,  and 
the  base  of  the  dyestuff  precipitated,  along  with  copper  oxide,  by 
addition  of  milk  of  lime,  and  the  precipitate  washed  to  remove 
soluble  salts.  It  is  then  suspended  in  water,  and  treated  with 
sulphuretted  hydrogen,  whereby  copper  sulphide  is  formed,  and 
being  insoluble  in  hydrochloric  acid,  the  violet  may  be  obtained  in 
solution  by  heating  the  precipitate  with  this  acid.  Finally,  the 
dyestuff  is  precipitated  from  the  acid  solution  by  salt,  and  purified 
by  repeated  solution  and  reprecipitation  by  salt. 

An  older  process,  now  abandoned,  possesses  interest  from  a 
theoretical  standpoint.  In  this  case  no  chlorine  compound  was 
used,  the  mixture  consisting  of  dimethylaniline,  copper  sulphate, 
acetic  acid,  and  sand.  The  violet  is  precipitated  from  the  solution 
of  the  melt  as  sulphate  by  sodium  sulphate.  The  absence  of 
chlorine  prevents  the  formation  of  the  insoluble  double  chloride, 
and  the  reduced  copper  compound  is  got  rid  of  as  insoluble  suboxide. 

The  role  played  by  the  phenol  in  the  modern  process  of  manu- 
facture has  not  been  explained,  but  it  is  certain  that  its  presence 
considerably  increases  the  yield  of  the  dyestuff. 

Methyl  violet  is  produced  by  action  of  other  oxidising  agents 
on  dimethylaniline,  such  as  iodine  and  chloranil.  According  to 
Brunner  and  Brandenburg  bromine  acts  on  dimethylaniline,  form- 
ing a  brominated  methyl  violet  [21].  On  the  other  hand,  the  dye- 
stuff  is  not  produced  by  oxidation  of  dimethylaniline  in  acid  solu- 
tion, with  lead  peroxide,  manganese  dioxide,  or  chromic  acid. 

As  yet,  the  chemistry  of  the  methyl-violet  process  is  little 
understood.  According  to  E.  and  O.  Fischer  [12],  a  methyl 
group  is  partly  oxidised,  and  the  formic  acid  produced  thereby 
serves  to  link  the  benzene  nuclei  together,  and  to  supply  the 
necessary  methane-carbon  atom.  As,  however,  the  formation  of 

i 


114  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

violet  is  difficult  to  follow,  it  is  not  easy  to  give  an  explanation  of 
the  reactions  involved  in  its  production. 

In  fact  O.  Fischer  and  Koerner  have  obtained  hexamethylpara- 
leucaniline  quantitatively  by  action  of  the  methyl  ether  of  ortho- 
f ormic  acid  on  dimethylaniline  [22] .  The  violet  from  dimethyl- 
aniline  and  chloranil  is  apparently  identical  with  the  ordinary  one 
obtained  by  the  copper  process  [23] . 

Methyl  violet  forms  amorphous  masses  with  a  green  lustre.  It 
,is  easily  soluble  in  water,  and  dyes  wool  and  silk  violet  from 
a  neutral  bath.  On  addition  of  a  mineral  acid,  the  solution  of  the 
violet  becomes  first  blue,  then  green,  and  finally  dirty  yellow. 

The  commercial  product  is  a  mixture,  consisting  chiefly  of 
pentamethyl-  and  tetramethyl-pararosaniline  with  some  hexa- 
methylpararosaniline. 

If  prepared  from  dimethylaniline  containing  monomethylaniline, 
the  violet  also  contains  lower  methylated  rosanilines. 

As  the  blue  shade  of  the  violet  increases  with  the  number  of 
methyl  groups,  the  bluest  brands  are  richest  in  hexamethyl  com- 
pounds. Blue  shades  of  violet  are  also  obtained  by  action  of 
benzyl  chloride  on  the  violet-base.  According  to  Fischer  the 
benzyl  group  does  not  attack  hexamethylpararosaniline,  only  the 
lower  methylated  products  yielding  benzylated  violets  [25] . 

The  dyestuffs  known  as  acid-violets  are  mostly  sulphonic  acids 
of  benzylated  methyl  violets. 

Methyl  violet  is  difficult  to  convert  into  sulphonic  acid  by  fuming 
sulphuric  acid ;  a  better  result  is  obtained  by  sulphonation,  and 
subsequent  oxidation  of  the  leuco-base.  Benzylated  violets,  how- 
ever; are  much  easier  to  sulphonate,  especially  in  form  of  their 
leuco-bases,  the  sulpho-group  probably  entering  the  benzene 
nucleus  of  the  benzyl  group.  Other  acid-violets  are  obtained  by 
methylation  and  benzylation  of  acid  magenta. 

Tetramethylpararosaniline  [24] . 


This  violet  dyestuff  was  prepared  by  Fischer  by  oxidation  of 
tetramethyltriamidotriphenylmethane ;  it  is  also  obtained  by 
partial  reduction  of  paranitro-malachite  green. 


TRIPHENYLMETHANE  DYESTUFFS.  115 

Acetyltetrametliylpararosaniline  [2 3], 


is  formed  by  oxidation  of  acetyltetramethylparaleucaniline.  It  is 
a  green  dyestuff,  and  on  treating  with  hydrochloric  acid  yields 
tetramethylpararosaniline. 

Pentamethylpararosaniline  [25]. 
/ceH4N(CH3)2 


The  pure  base  is  obtained  by  saponification  of  its  diacetyl  deri- 
vative with  hydrochloric  acid.  The  hydrochloride  is  a  constituent 
of  commercial  methyl  violet. 

DiacetylpentametJiylpararosaniline  [25]. 
[(CH3)2NC6H4]2=C— C6H4NCH3 .  C2H3O 


oa 


May  be  obtained  by  treating  the  crude  base  of  methyl  violet  with 
acetic  anhydride.  It  is  a  colourless  base,  and  gives  a  green  salt 
with  acetic  acid.  This  fact  is  not  easily  understood  unless  under 
the  assumption  that  one  acetyl  group  splits  off,  and  the  oxygen 
atom  of  the  carbinol  group  is  eliminated. 

Hexamethylpararosaniline  [23,  25,  26]. 
Cl 

[  (CH3)  2NC6H4]  2  =  C— C6H4N(CH3)  2 

This  dyestuff  is  known  in  commerce  as  Crystal  Violet,  and  also 
occurs  in  Methyl  Violet.  It  is  obtained  by  action  of  dimethyl- 
aniline  on  tetramethyldiamidobenzophenone  : 

(CH3)2NC6H4— CO— C6H4N(CH3)2 

in  presence  of  a  dehydrating  agent,  according  to  the  equation 

C17H20N20  +  C8HUN,HC1  =  C25H30N3C1  +  H2O. 
This  is  effected  on  a  large  scale   in  one  operation,    phosgene 
(COC12)  being  allowed  to  act  on  dimethylaniline  in  presence  of 


116  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

zinc  chloride,  and  further  is  formed  by  action  of  perchlormethyl- 
formiate  on  dimethylaniline  in  presence  of  aluminium  chloride  or 
zinc  chloride.  It  is  also  produced  by  heating  its  methyl  chloride 
or  methyl  iodide  compound  (methyl  green)  to  110°-120°. 

The  hydrochloride  and  zinc  double  salt  form  lustrous  green 
crystals. 

The  hydriodide  and  picrate  are  sparingly  soluble. 

On  reduction  it  yields  hexamethylleucaniline,  which  forms 
leaflets,  M.P.  173°. 

Hexaethy  lp  ararosanilin  e  . 

r  -i      C  --  ^C1 

[(C2H5)2-X-C6H4]2-C-C6H4-N(C2H5)2. 

This  dyestuff  comes  into  commerce  as  Ethyl  Purple,  and  is  pre- 
pared by  the  action  of  phosgene  on  diethyl  aniline.  It  dyes  bluer 
shades  than  Crystal  Violet. 

Azo-Grcen. 

OH 

(CH3L-N—  C6H4-C/C«H*—  N=N—  C6H3/CO 
|VC6H4-N(OH8)2 
I  --  JL_  --  —  0 


Although  containing  an  azo-group,  the  tinctorial  properties  of 
this  dyestuff  are  due  to  its  derivation  from  triphenyl-carbinol.  It 
is  obtained  by  combining  the  diazo-compound  from  metamidotetra- 
methyldiamido-triphenylmethane  with  salicylic  acid.  It  dyes 
chromed  wool  a  bright  greenish-yellow  shade.  The  corresponding 
paramido-compound  gives  a  blue  dyestuff. 

Metlnjl  Green  [19,  25]. 

/C6H4N(CH3)2CH3C1 

»/    *      4      v          6U          6 


(Chlormethylate  of  Hexainethylpararosaniline  Chloride.) 

This  chloride  or  the  corresponding  iodide  is  formed  by  the  action 
of  methyl  chloride  or  iodide  on  commercial  methyl  violet.  The 
tetra-  and  penta-methylpararosanilines  are  converted  into  hexa- 
methylrosaniline  ;  the  latter  adding  on  one  molecule  of  methyl 
chloride  or  iodide. 

On  a  large  scale  methyl  chloride  is  used.     A  slow  stream  of  the 


TRIPHENYLMETHANE  DYESTUFFS.  117 

gas  is  passed  through  an  alcoholic  solution  of  methyl  violet  heated 
to  40°,  and  kept  neutral  by  addition  of  soda.  Autoclaves  are  un- 
necessary, as  methyl  chloride  is  sufficiently  soluble  in  alcohol  and 
no  pressure  is  produced. 

The  alcohol  is  then  distilled  off,  and  the  residue  dissolved  in 
water,  and  unaltered  violet  precipitated  by  addition  of  soda  or 
chalk  and  common  salt. 

The  pure  zinc  double  salt  of  methyl  green  is  then  precipitated 
by  adding  zinc  chloride ;  the  precipitate  being  sometimes  washed 
with  alcohol  to  remove  any  violet  present.  In  commerce  this  zinc 
double  salt  is  generally  met  with  in  the  form  of  brilliant  green  leaflets. 

The  iodide,  C26H33N3I2,  forms  green  needles  easily  soluble  in 
water  [18]. 

Thejozcr«/e,C26H33N3[(C6H3)(NO2)3OH]2,  is  insoluble  in  water, 
sparingly  soluble  in  alcohol. 

The  base,  C26H35TsT3O2,  is  obtained  by  treating  the  chlorine  or 
iodine  compound  with  silver  oxide.  It  is  colourless,  and  its 
alcoholic  solution  remains  colourless  on  acidifying,  the  formation  of 
a  green  salt  only  taking  place  on  warming.  The  salts  of  methyl 
green  decompose  at  110°  to  120°,  methyl  chloride  or  iodide  splitting 
off,  and  leaving  a  violet  residue  of  hexamethylrosaniline  chloride. 

An  analogous  green  is  the  brom-ethylate  obtained  by  the  action 
of  ethyl  bromide  on  methyl  violet.  The  composition  of  the  com- 
mercial zinc  double  salt  (ethyl  green)  is  probably 

C25H30N3ClC2H5BrZnCl2. 

An  advantage  of  this  ethyl  green  is  that  its  shade  is  yellower  than 
that  of  methyl  green.  Methyl  and  ethyl  greens  dye  silk  directly, 
and  cotton  prepared  with  tannic  acid.  Wool  cannot  be  dyed 
directly,  and  is  either  previously  mordanted  with  sulphur  by  a  bath 
of  thiosulphate  of  soda,  or  dyed  in  a  bath  of  methyl  green  made 
alkaline  with  ammonia.  Fibres  dyed  with  these  greens  become 
violet  on  heating,  and  this  reaction  serves  for  their  identification. 
At  present  methyl  and  ethyl  green  are  scarcely  ever  used,  having 
been  replaced  by  the  cheaper  and  stronger  benzaldehyde  greens. 

The  green  colour  of  a  compound  appears  to  require  the  presence 
of  an  ammonium  group,  and  an  amido-group  not  in  combination 
with  an  acid.  Benzaldehyde  green,  for  example,  fulfils  these  con- 
ditions. In  methyl  violet,  an  ammonium  group  and  two  methy- 
lated amido-groups  are  present,  and  as  long  as  the  latter  are  not 
in  combination  with  an  acid  the  compound  is  violet.  When,, 


118  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

however,  one  of  them  is  saturated  by  an  acid,  the  colour  changes 
to  green,  but  the  green  salts  are  unstable,  and  are  decomposed  by 
water.  Stable  green  dyestuffs  are  formed,  if  the  acid  is  replaced 
by  methyl  chloride,  the  same  effect  being  produced  by  the  intro- 
duction of  an  ethyl  group.  It  appears,  therefore,  that  the  neutral- 
isation of  the  basic  properties  of  the  third  nitrogenous  group  has 
the  same  effect  as  its  entire  removal  would  have. 

TriamidodiplienyltolylcarUnol  [12,  28]. 
(ROSANILINE,  MAGENTA,  FUCHSINE.) 


OH 

Rosaniline,  a  homologue  of  pararosaniline,  is  formed  by  oxida- 
tion of  equal  molecules  of  orthotoluidine,  paratoluidine,  and 
aniline.  As  oxidising  agents,  stannic  chloride,  mercuric  chloride 
or  nitrate,  arsenic  acid,  or  nitrobenzene  may  be  used.  Mercuric 
nitrate,  arsenic  acid,  and  nitrobenzene  have  been  applied  on  a  large 
scale  ;  but  at  present  the  two  latter  are  the  only  oxidants  used 
technically.  The  arsenic  acid  process  is  carried  out  in  a  boiler 
fitted  with  a  stirrer,  and  connected  with  a  cooling-  worm.  Aniline 
of  approximately  the  above  composition  (aniline  for  red)  and 
syrupy  arsenic  acid  (containing  about  70  per  cent,  arsenic  anhy- 
dride) are  introduced,  and  the  mixture  is  heated  to  170°-180°. 
Part  of  the  aniline  oil  used  distils  over  during  the  operation, 
which  generally  lasts  8  to  10  hours.  As  soon  as  the  melt  has 
attained  a  certain  condition,  it  is  allowed  to  flow  out,  and  after 
cooling  is  broken  up.  It  is  then  boiled  with  water  in  a  closed 
vessel  under  pressure,  the  arsenic  and  arsenious  acids  being  at 
the  same  time  partly  neutralised  by  addition  of  lime.  After 
filtering,  the  rosaniline  hydrochloride  is  separated  from  the  filtrate 
by  addition  of  salt.  It  is  purified  by  recrystallisation.  Magenta 
prepared  by  this  process  generally  contains  arsenic.  In  the  nitro- 
benzene process,  aniline  for  red  is  heated  with  hydrochloric  acid, 
nitrobenzene,  and  iron,  the  process  being  carried  out  in  much  the 
same  manner  as  above.  The  iron  serves  to  start  the  process,  by 
forming  ferrous  chloride,  which  is  oxidised  'to  ferric  chloride  by 
the  nitrobenzene,  which  latter  salt  in  turn  effects  the  oxidation  of 
the  aniline. 


TRIPHENYLMETHANE  DYESTUFFS.  119 

Nitrobenzene  appears  to  take  no  part  in  the  formation  of  ros- 
aniline,  and  simply  acts  as  oxidant,  being  converted  to  dyestuffs 
of  the  induline  class.  When  nitrobenzene  is  replaced  by  chlor- 
nitroberizene,  rosaniline  is  produced,  and  not,  as  might  be  expected, 
a  chloro-derivative.  Dyestuffs  of  the  rosaniline  series  are  formed 
by  oxidation  of  numerous  bases  in  presence  of  aniline  and  parato- 
luidine.  Rosen stiehl  and  Gerber  divide  the  homologues  of  aniline 
into  three  classes,  according  to  their  behaviour  on  oxidation  with 
arsenic  acid. 

The  first  class  includes  bases  which  do  not  yield  a  magenta  on 
oxidation  alone,  but  do  if  oxidised  in  presence  of  aniline.  These 
bodies  are  paratoluidine,  asymmetric  a-metaxylidine,  cumidine, 
and  amidotetra-  and  amidopenta-methylbenzene. 

The  second  class  comprises  those  bases  which  yield  no  magenta 
on  oxidation  with  arsenic  acid,  but  do  so  if  oxidised  in  presence  of 
a  base  of  the  first  class.  These  bases  are  aniline,  orthotoluidine, 
and  y-metaxylidine.  The  bases  of  the  third  class,  metatoluidine 
and  /3-metaxylidine,  do  not  yield  magenta  under  any  conditions. 

In  the  first  class,  one  methyl  group  is  in  the  para  position  to  the 
amido-group,  while  in  the  second  and  third  classes  the  para  position 
is  free.  In  the  second  class  the  groups  are  in  the  ortho  position, 
and  in  the  third  class  in  the  meta  position  to  the  amido-group. 
E.  and  O.  Fischer's  experiments  have  proved  that,  in  the  simplest 
rosaniline,  the  three  amido-groups  are  in  the  para  position  to  the 
fundamental  carbon  atom.  The  complete  analogy  of  the  homo- 
loguous  rosanilines  with  the  first  having  been  proved,  it  can  be 
readily  understood  why  the  members  of  the  first  group,  when 
oxidised  by  themselves  or  with  each  other,  do  not  yield  rosaniline, 
but  do  so  in  presence  of  aniline. 

In  the  bases  of  the  second  class,  the  para  position  is  free,  and 
one  or  two  ortho  positions  are  occupied.  It  is  clear  that  these 
bases  cannot  yield  rosanilines  unless  they  are  oxidised  with  a  base 
of  the  first  group.  Neither  can  the  bases  of  the  first  class  pro- 
duce magentas,  but  no  reasons  yet  given  can  explain  why  they 
should  not  be  able  to  produce  rosanilines,  when  oxidised  with  other 
members  of  the  first  class.  The  experiments  of  Monnet,  Reverdin. 
and  Noelting  and  O.  Fischer  and  Koch  have,  however,  confirmed 
this  experiment.  Noelting  has  recently  extended  our  knowledge 
of  the  behaviour  of  the  homologues  of  aniline  in  this  direction. 
He  examined  bases  in  which  both  the  meta  and  ortho  positions  are 
occupied,  and  found  that  such  bases  do  not  yield  magenta  under  any 


120  CHEMISTRY  OF  ORGANIC  DYESTTJFFS. 

conditions,  and  therefore  belong  to  the  third  class.  Metamethy- 
lated  paratoluidines  yield  magenta  on  oxidation  in  presence  of 
aniline,  whether  the  ortho  position  be  occupied  or  not. 

The  investigations  on  this  subject  are  best  summarised  as 
follows  : — All  paramethylated  anilines,  paratoluidine,  a-metaxy- 
lidine,  a-orthoxylidine,  mesidine,  pseudocumidine,  isocumidine, 
the  cnmidine  of  Noelting  and  Forel,  isoduridine,  phrenidine,  and 
pentamethylamidobenzene  yield  magentas  on  oxidation  with  two 
molecules  of  aniline,  orthotoluidine,  or  v-metaxylidine,  but  do  not 
if  oxidised  with  para  free  but  methylated  anilines  as  metatoluidine, 
paraxylidine,  v-orthoxylidine,  s-metaxylidine,  the  cumidines  of 
Edler  and  Mayer,  and  crystallised  duridine. 

The  commercial  dyestuff  is  the  hydrochloride  of  rosaniline ;  the 
acetate,  however,  is  also  sometimes  met  writh.  The  free  base  is 
also  prepared  for  the  manufacture  of  aniline  blue. 

Rosaniline-lase  [28]. 
C20H21N30. 

Free  rosaniline  crystallises  in  colourless  leaflets,  which  become 
red  on  exposure  to  the  air.  It  is  sparingly  soluble  in  cold  water, 
somewhat  more  easily  in  hot  water,  and  still  more  easily  in 
alcohol.  It  is  sparingly  soluble  in  ether. 

Rosaniline  is  capable  of  expelling  ammonia  from  a  boiling  solu- 
tion of  ammonium  chloride,  while  in  the  cold  rosaniline  is  preci- 
pitated from  a  solution  of  its  salts  by  ammonia. 

The  base  is  obtained  technically  by  boiling  the  hydrochloride 
(magenta)  with  the  calculated  amount  of  lime  or  caustic  soda,  and 
a  large  quantity  of  water.  The  filtered  solution  deposits  the  base 
on  coobng,  in  form  of  colourless  leaflets  which  become  brownish 
on  exposure  to  air. 

By  heating  with  water  to  235°,  rosaniline  decomposes,  yielding 
phenol,  ammonia,  a  base  C20H20N2O2,  M.P.  176°,  and  an  acid 
C20H19KO3  [25].  At  270°  ammonia,  phenol,  and  dioxybenzo- 
phenone  HO— C6H4COC6H4— HO  are  formed  [26]  . 

The  salts  [24]  of  rosaniline,  like  those  of  pararosaniline,  are 
formed  with  a  simultaneous  elimination  of  water.  The  monoacid 
salts  have  an  intense  red  colour ;  the  diacid  salts  are  yellowish- 
brown  [24].  The  salts  are  converted  into  a  tertiary  diazo- 
compound  by  the  action  of  nitrous  acid  [12]. 

Hydrochloride,  C20H19N3,HC1  +  4H20,  occurs  as  large  octohedra 


TRIPHENYLMETHANE  DYESTUFFS.  121 

or  rhombic  tables,  which  have  a  green  metallic  reflex.  It  is  with 
difficulty  soluble  in  cold  water,  easily  in  hot  water  and  alcohol. 

Acid  salt,  C20H19N3,  (HC1)3,  forms  brownish-yellow  needles, 
easily  soluble  in  water,  and  decomposed  by  an  excess,  or  at  100°. 

Platinum  salt,  (C2oH2oN3Cl2)(PtCl4)3. 

Hydro  bromide,  C20H19N3,HBr,  is  sparingly  soluble. 

Sulphate,  (C20H19N3)2H2SO4,  forms  brilliant  green  crystals, 
sparingly  soluble  in  water. 

Acetate,  C2oH19N3,C2H4O2,  forms  large  green  crystals,  easily 
soluble  in  water. 

Pier  ate,  C20H19N3,C6H2(NO2)3OH,  forms  needles,  sparingly 
soluble  in  water. 

The  tannate  forms  a  red  precipitate  insoluble  in  water. 

Rosaniline  and  pararosaniline  form  colourless  unstable  com- 
pounds with  sulphurous  acid  and  bisulphites.  These  compounds 
react  with  aldehydes,  forming  peculiar  dyestuffs  (Detection  of 
Aldehydes  [29]). 

Eosanilinesulphonic  Acid  [30], 
(MAGENTA  S,  ACID  MAGENTA.) 

By  the  action  of  strong  fuming  sulphuric  acid  on  magenta  at 
120°,  a  sulphonic  acid,  probably  the  disulphonic  acid,  is  formed. 
This  acid  has  an  intense  red  colour,  and  the  solutions  of  its  salts 
are  not  turned  yellow  by  acids  like  those  of  magenta.  The  neutral 
salts,  with  the  alkalies  and  metallic  oxides,  are  colourless,  the  acid 
salts  being  red.  Both  are  easily  soluble  in  water,  and  difficult  to 
crystallise.  From  the  colour  of  the  acid  it  is  probable  that  the 
sulpho-  and  amido-groups  are  combined  to  form  a  salt,  while  the 
colourless  salts  contain  the  carbinol  group. 

Rosanilinesulphonic  acid  dyes  wool  and  silk  from  an  acid  bath, 
and  finds  extensive  application  in  dyeing. 

Tetrabromrosaniline  [31] 

is  formed  by  the  action  of  bromine  on  rosaniline.  It  is  a  colour- 
less base,  forming  violet  salts. 

At  present  the  researches  of  E.  and  O.  Fischer  and  others  have 
led  to  some  confusion  as  to  the  exact  composition  of  the  methyl- 
rosanilines  examined  by  Hofmann.  If  methyl  green  is  hepta- 


122  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

methyl pararosaniline,  iodine  green  is  not  penta-  but  heptamethyl- 
rosaniline,  and  the  violet  formed  on  heating  is  hexamethylrosa- 
niline.  The  analytical  results  obtained  by  Hofmann  scarcely 
admit  of  this  interpretation.  In  the  present  work  these  bodies 
are  described  under  the  older  formulae,  with  the  hope  that  further 
researches  may  elucidate  the  matter. 

Trimethylrosaniline  [2  8], 

C20H18(CH3)3N30. 

The  hydriodide,  CosHogNgljis  formed  by  heating  rosaniline  with 
methyl  iodide  and  methyl  alcohol.  It  is  a  violet  dyestuff  sparingly 
soluble  in  water. 

Tetramethylrosanilin e  [28], 

C20H17(CH3)4N30, 

is  obtained  by  heating  iodine  green  to  120°.  The  iodide, 
C24H28N3I,  forms  long  bluish-violet  needles. 

Pentamethylrosaniline  [32].     (IODINE  GKEEN.) 

The  iodide,  C2oH17(CH3)4N3l,CH3I  +  H2O,  is  prepared  by  heat- 
ing rosaniline  with  methyl  iodide  and  methyl  alcohol  to  100°.  It 
is  freed  from  any  violet  dyestuff  present  in  the  same  manner  as 
methyl  green. 

The  iodide  forms  metallic  prisms  easily  soluble  in  water.  When 
heated  to  100°-120°  methyl  iodide  splits  off,  leaving  tetramethyl- 
pararosaniline. 

The  zinc  double  salt,  C25H31N3Cl2,ZnCl2,  forms  large  green 
crystals.  Its  solutions  are  turned  yellowish-green  by  acids. 

The  picrate,  C25H29N3C6H3(NO2)3O,  forms  prisms  with  a  coppery 
reflex,  which  are  insoluble  in  water  and  sparingly  soluble  in  alcohol. 

Before  the  introduction  of  methyl  green,  iodine  green  was  ex- 
tensively used  in  dyeing. 

Hexamethylrosaniline  [32]. 

The  iodide,  C20H14(CH3)6N3I,  is  formed  along  with  octomethyl- 
leucaniline  by  heating  iodine  green  with  methyl  alcohol  in  a  sealed 
tube  to  100°.  It  forms  brownish-green  needles,  insoluble  in  water 
and  sparingly  soluble  in  alcohol.  It  is  a  violet  dyestuff. 


TRIPHENYLMETHANE  DYESTUFFS.  123 

Triethylrosaniline  [28].     (HOFMANN'S  VIOLET.) 

C20H18(C2H5)3N30. 

The  iodide,  C26H35N3I2,  is  obtained  by  heating  rosaniline  with 
ethyl  iodide  and  alcohol.  It  forms  brilliant  green  needles,  soluble 
in  alcohol  and  sparingly  so  in  water.  It  was  formerly  manufac- 
tured on  a  large  scale. 

Tetraetliylrosaniline  [28]. 
The  iodide  has  the  formula  C2oH16(C2H5)4N3L 

Tribenzylrosaniline-metliyliodide^ 

C2oHi6(C7H7)  3N3CH3I, 

is  prepared  by  treating  rosaniline  with  benzyl  chloride,  methyl 
iodide,  and  methyl  alcohol.  It  forms  green  needles  insoluble  in 
water  [33]. 

Acetylrosaniline  [34], 
C20H18(C2H30)N3,  " 

is  formed  when  rosaniline  hydrochloride  is  heated  with  acetamide. 
It  dissolves  in  alcohol  with  a  red  colour,  and  forms  violet  salts. 

Triacetylrosaniline  [35], 
CsoHigNg  (C2H3O)3, 

and  Tribenzoylrosaniline  [35], 

C20H16N3(C7H50)3, 

are  obtained  by  the  action  of  acetyl  chloride  and  benzoyl  chloride 
respectively  on  rosaniline.  They  are  colourless  bases  forming 
orange  salts. 

Compounds  of  rosaniline  with  aldehydes  have  been  described  by 
II.  Schiff  (Ann.  cxl.  p.  101). 


The  yield  of  magenta  obtained  on  a  large  scale  by  either  of  the 
processes  already  described  is  very  poor,  and  seldom  exceeds  33 
per  cent,  of  the  weight  of  the  bases  employed.  A  large  quantity 
of  bye-products  is  formed,  and  little  is  known  as  to  their  nature. 
A  constant  product  of  the  arsenic  acid  process  is  a  small  quantity 


124  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

of  chrysaniline.  Besides  this,  various  violet  and  bluish-black  pro- 
ducts are  formed,  some  of  which  are  soluble  in  water,  some  in 
alcohol,  and  others  are  totally  insoluble.  Some  of  these  dyestuft's 
dissolve  and  remain  in  the  mother-liquor  of  the  magenta,  but  by 
far  the  greater  part  occur  in  the  insoluble  residue.  From  the  latter 
Girard,  Delaire,  and  Chappotot  [36]  have  isolated  three  bases,  viz. : — 
mauvaniline,  C19H17N3,  violaniline,  C18H15N3,  and  chrysotoluidine, 
C21H2iN3.  However,  sufficient  analytical  data  are  not  forthcoming 
to  support  these  formulae,  and  it  is  doubtful  whether  the  products 
examined  were  really  chemical  individuals.  Possibly  violaniline  is 
identical  with  the  simplest  induline,  and  chrysotoluidine  with 
chrysaniline,  especially  as  dyes  of  the  induline  series  occur  in  the 
the  magenta-residues  (see  Indulines). 


Aniline  Blue  [37]. 

Aniline  reacts  with  rosaniline  at  180°  in  presence  of  certain 
organic  acids,  ammonia  being  evolved,  and  phenyl-groups  entering 
into  the  rosaniline  molecule.  According  to  the  number  of  phenyl- 
groups  introduced,  the  shade  of  the  compound  produced  varies 
from  violet  to  pure  blue.  It  is  not  possible  to  introduce  more  than 
three  phenyl-groups  into  the  rosaniline  molecule.  Acetic  acid, 
benzoic  acid,  and  stearic  acid  have  been  used  technically,  but  at 
present  benzoic  acid  alone  is  used,  as  by  its  aid  the  best  results  are 
obtained  both  as  regards  yield  and  shade  of  blue  (greenish).  The 
action  of  organic  acids  in  the  blue  process  has  not  yet  been  ex- 
plained. Rosaniline  heated  with  aniline  without  an  organic  acid 
does  not  yield  a  blue ;  a  blue  is,  however,  formed  from  rosaniline 
and  paratoluidine.  Only  a  minute  quantity  of  benzoic  acid  is 
required  to  effect  the  formation  of  blue,  but  in  presence  of  a 
larger  quantity  the  results  are  better,  and  the  process  is  more 
rapid.  At  the  end  of  the  reaction,  benzoic  acid  remains  in  the 
melt  unaltered,  and  may  be  almost  entirely  recovered  by  extrac- 
tion with  alkali. 

The  amount  of  aniline  used  in  the  manufacture  of  blue  is  of 
great  importance.  In  presence  of  a  large  excess  of  aniline  the 
phenylation  is  more  complete  and  rapid  than  when  a  small  quan- 
tity is  used.  For  production  of  pure  triphenyl rosaniline  (green 
shade  of  blue)  a  large  excess  of  aniline  is  used  (ten  times  the 
theoretical  amount)  along  with  a  correspondingly  large  amount  of 


TRIPHENYLMETHAXE  DYESTUFFS.  125 

benzole  acid.  The  higher  homologues  of  aniline,  especially  ortho- 
toluidine,  give  redder  shades  of  blue,  and  it  is  therefore  necessary 
to  use  an  aniline  as  pure  as  possible.  It  is  required  that  commer- 
cial "  aniline  for  blue  "  should  distil  within  one  degree,  and  is  thus 
almost  chemically  pure  aniline.  For  the  manufacture  of  a  reddish 
shade  of  blue,  smaller  quantities  of  benzoic  acid  and  aniline  are 
used,  and  a  less  pure  aniline-oil  is  applicable.  On  a  large  scale 
aniline  blue  is  prepared  approximately  as  follows  : — 

The  mixture  of  the  requisite  quantities  of  rosaniiine  base,  ben- 
zoic acid,  and  aniline  is  brought  into  a  vessel  fitted  with  stirrer 
and  distilling  arrangement,  and  heated  to  the  boiling-point  of  the 
aniline.  As  the  blue  is  contained  in  the  melt  in  form  of  the 
colourless  base  the  progress  of  the  reaction  cannot  be  ascertained 
by  simple  inspection.  For  this  purpose  portions  are  removed  from 
time  to  time,  and  dissolved  in  alcohol  and  acetic  acid,  the  operation 
being  interrupted  as  soon  as  the  test  shows  that  the  desired  shade 
has  been  reached.  According  to  the  shade  of  blue  required,  the 
process  may  last  two  to  four  hours,  but  if  the  heating  is  protracted, 
some  of  the  blue  is  liable  to  be  destroyed. 

On  partly  saturating  the  melt  with  concentrated  hydrochloric 
acid,  the  hydrochloride  of  tripheriylrosaniline  separates  out  almost 
in  a  state  of  chemical  purity,  while  impurities  remain  dissolved 
in  the  concentrated  solution  of  aniline  in  aniline  hydrochloride. 
This  latter  is  separated  and  saturated  with  dilute  acid,  and  the 
precipitate  is  worked  up  for  inferior  blue.  This  method  of  purifi- 
cation has  completely  replaced  the  older  process  with  alcohol. 

The  salts  of  the  lower  phenylated  rosanilines  dissolve  easily  in 
alcohol,  while  those  of  triphenylrosaniline  are  very  sparingly 
soluble.  A  very  large  number  of  marks  of  blue  come  into  com- 
merce, the  shades  being  influenced  firstly  by  the  degree  of  phenyla- 
tion,  and  secondly  by  the  number  of  sulpho-groups  introduced  for 
the  production  of  soluble  blue.  Other  brands,  again,  are  obtained 
from  the  lower  quality  of  blue  already  mentioned. 


i.  MonophenylrQsaniline. 

C20H20N3(C6H5)0. 

The  hydrochloride  forms  brilliant  bronzy  crystals,  soluble  in 
alcohol  with  a  reddish- violet  colour  [39] . 


126  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

ii.  Diphenylrosaniline. 

C20H19N3(C6H5)20. 
This  base  forms  bluish- violet  salts  [28,  38]. 

iii.  Triphenylrosanilme.     (ANILINE  BLUE.) 

C20H18N3(C6H5)30. 

The  free  base  is  colourless  and  easily  soluble  in  alcohol  [28, 
37,  38] . 

^hehydrochloride,  C20H17N3(C6HJ3HC1,  is  the  technical  product 
obtained  first  in  the  fractional  precipitation  of  the  blue  melt  with 
hydrochloric  acid.  In  this  state  it  forms  brilliant  green  crystals, 
insoluble  in  water  and  sparingly  soluble  in  hot  alcohol.  Aniline 
dissolves  it  somewhat  more  easily.  The  alcoholic  solution  has  a  pure 
blue  colour.  Some  of  this  product  is  used  as  "  spirit-blue,"  but 
by  far  the  greater  quantity  is  used  for  the  manufacture  of  soluble' 
blues.  Triphenylrosaniline  salts  dissolve  in  sulphuric  acid  with  a 
brown  colour. 

The  sulphate  (C20H16N3(C6H5)3H2S04)  is  almost  insoluble  in 
alcohol. 

iv.  Sulplionic  Acids  of  Triphenylrosaniline. 

The  difficulties  encountered  in  the  sulphonation  of  rosaniline 
are  altogether  absent  in  that  of  the  phenylated  rosanilines.  A 
monosulphonic  acid  is  formed  by  the  action  of  concentrated  sul- 
phuric acid  at  a  comparatively  low  temperature,  while  by  a  more 
energetic  sulphonation  two,  three,  and  even  four  sulpho-groups 
may  be  introduced  into  the  molecule. 

From  the  foregoing  it  appears  probable  that  the  sulpho-groups 
enter  the  phenyl  groups  and  not  the  rosaniline  nucleus. 

The  sulphonic  acids  are  all  amorphous,  and  possess  a  blue  colour. 
The  salts  of  the  acids  are,  on  the  contrary,  colourless  and  probably 
carbinol  derivatives. 

Monosulphonic  Acid. 
C38H30N3S03H. 

This  is  the  first  product  of  the  action  of  sulphuric  acid  on 
aniline  blue.  The  free  acid  is  obtained  as  a  blue  amorphous 


TRIPHENYLMETHANE  DYESTUFFS.  127 

precipitate,  which  is  insoluble  in  water.  The  salts  are  colourless  or 
nearly  so,  are  easily  soluble  in  water,  and  cannot  be  crystallised. 
The  sodium  salt  forms  the  "  alkali  blue  "  of  commerce. 

This  salt,  unlike  those  of  other  sulphonic  acids,  may  be  fixed 
on  wool  and  silk  from  a  slightly  alkaline  bath.  It  is  probable  that 
the  basic  groups  of  rosaniline  effect  this  fixation.  The  shade  ob- 
tained is  not  strong,  but  on  development  with  dilute  acid,  whereby 
the  free  sulphonic  acid  is  liberated,  a  good  blue  shade  is  obtained. 
Alkali  blue  finds  its  principal  application  in  wool-dyeing. 


Disulphonic  Acid, 

C38H29N3(S03H)2, 

is  a  product  of  the  further  action  of  sulphuric  acid  on  the  above 
acid.  It  is  soluble  in  pure  water,  but  insoluble  in  dilute  sulphuric 
acid,  and  may  therefore  be  precipitated  from  the  sulphuric-acid 
solution  by  water. 

It  forms  two  series  of  salts  with  bases — acid  salts,  which  have  a 
coppery  reflex,  and  neutral  salts,  which  are  colourless.  The  acid 
sodium  salt  is  a  commercial  product,  and  is  known  as  "  water  blue 
for  silk." 

Tri-  and  Tetra-sulphonic  Adds. 

These  bodies  result  by  continued  action  of  sulphuric  acid  at  a 
higher  temperature. 

They  are  not  precipitated  from  an  acid  solution  by  water^  and 
thus  differ  from  the  disulphonic  acid.  In  order  to  isolate  them, 
the  sulphuric-acid  solution  is  neutralised  with  chalk,  and  the  pre- 
cipitated calcium  sulphate  filtered  off.  The  solution  of  lime-salt 
is  then  converted  into  sodium-salt. 

The  dyestuff  known  as  "  soluble  blue  for  cotton  "  is  probably  a 
mixture  of  both  acids,  or  rather  of  their  acid  sodium-salts. 

All  the  "  soluble  blues "  are  dyed  on  wool  and  silk  from  a 
bath  containing  sulphuric  acid.  Cotton  is  previously  mordanted 
with  alum  and  soap,  or  with  tannin  and  tartar  emetic. 

Another  blue  is  obtained  by  the  action  of  aniline  and  benzoic  acid 
on  pararosaniliue.  This  product  is  valued  for  the  pure  greenish 
shade  which  it  produces,  and  it  has  recently  found  extensive  appli- 
cation, and  appears  to  have  almost  displaced  diphenylamine  blue. 


128  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Homologues  of  aniline  blue  have  been  prepared  by  the  action 
of  toluidines  on  rosaniline.  They  possess  a  dull  reddish  shade. 

Naphthylrosanilines  are  formed  by  action  of  the  naphthylamines 
on  rosaniline,  but,  like  the  above,  possess  no  technical  interest. 

Diphenylamine  Slue. 
Girard  and  Delaire  (Jahresber.  1867,  p.  695). 

Dyestuffs  of  a  very  pure  blue  shade  are  formed  by  the  action  of 
oxalic  acid  or  of  hexachloride  of  carbon  (C2C16)  on  diphenylamine. 
On  a  large  scale  diphenylamine  blue  is  prepared  by  heating 
diphenylamine  with  oxalic  acid  to  110°-120°.  The  dyestuff 
formed,  which  amounts  to  only  10  per  "cent,  of  the  diphenylamine 
employed,  is  purified  by  repeated  treatment  with  alcohol.  It  comes 
into  commerce  in  the  form  of  its  higher  sulphonic  acids  (soluble 
blue),  and  finds  its  principal  application  in  silk-  and  cotton-dyeing. 

Similar  dyestuffs,  probably  identical  with  diphenylamine  blue, 
are  formed  by  treating  methyldiphenylamine  with  oxidising  agents, 
as,  for  example,  with  chloranil  [15] . 

A  dyestuff  named  Bleu  de  Mulhouse  was  prepared  by  Gros- 
Renaud  and  Schaeffer  by  the  action  of  alkaline  shellac  solution  on 
rosaniline. 

Persoz,  Deluyne,  and  Calvetet  obtained  (1861)  a  soluble  blue  dye- 
stuff  by  the  action  of  anhydrous  stannic  chloride  on  aniline  (pure  ?) . 
The  composition  of  this  compound  is  not  known,  neither  has  it 
been  applied  in  practice  [41] . 

Aldehyde  Green  [43,  70,  71]. 

On  treating  rosaniline  with  aldehyde  and  sulphuric  acid,  a  blue 
dyestuff  is  formed,  which,  on  treatment  with  sodium  thiosulphate 
in  acid  solution,  yields  aldehyde  green.  For  its'  preparation,  a 
mixture  of  rosaniline,  aldehyde,  and  sulphuric  acid  is  heated,  till 
the  product  produces  a  blue-violet  solution  with  water.  It  is  then 
poured  into  a  very  dilute  solution  of  sodium  thiosulphate.  Sulphur 
and  a  grey  compound  separate,  while  the  green  remains  dissolved. 
It  may  be  precipitated  by  addition  of  zinc  chloride  or  acetate  of 
soda ;  in  one  case  a  zinc  double  salt,  and  in  the  other  a  free  base, 
is  obtained. 

The  chemistry  of  the  reactions  taking  place  in  the  preparation 
of  aldehyde  green  has  been  studied  in  detail  with  pararosaniline. 


TRIPHENYLMETHANE  DYESTUFFS.  129 

In  the  first  stages  of  the  reaction   a  blue  dyestuff,  the  so-called 
aldehyde  blue.,  is  formed,  along  with  a  green  dyestuff. 

This  blue  has  the  composition  of  an  anhydro-aldol-pararosani- 
line, 

/C6H4-N=CH-CHo-CHOH-CH3 
OH—  C-C6H4  -  N=CH  -  CHo"-  CHOH  -  CH3 


and  is  incapable  of  yielding  the  green  on  treatment  with  a  thio- 
sulphate.  The  green  dyestuff  formed  at  the  same  time  is  a  quin- 
aldine  derivative  of  the  above  dyestuff,  and  has  the  constitution 


^CH 

;-N=C-CH3 

f4-  N=CH-CH2-CHOH-CH3 
C6H4-  N=CH-CH2-CHOH-CH3. 

The  thiosulphate  employed  in  the  reaction  enacts  two  functions. 
It  separates  the  above  blue  dyestuff,  and  at  the  same  time  converts 
the  green  dyestuff  into  a  new  compound,  containing  sulphur,  which 
is  faster  to  light  and  dyes  a  better  shade  than  the  original  green. 
Two  processes  were  originally  in  vogue  for  the  production  of  alde- 
hyde green.  The  process  of  Lucius  consists  in  treating  the  mix- 
ture obtained  by  the  action  of  aldehyde  and  sulphuric  acid  on  rosa- 
niline  with  sulphuretted  hydrogen  and  then  with  sulphurous  acid, 
while  in  that  of  Usebe  the  agent  employed  is  a  thiosulphate.  The 
green  dyestuffs  obtained  in  these  processes  are  both  derived  from 
the  above  green,  but  differ  in  composition.  The  green  obtained  in 
Lucius's  process  contains  two  atoms  of  sulphur,  while  that  of 
Usebe  only  contains  one.  Their  constitutions  are  expressed  by  the 
following  formulae  : — 

CH  =  CH 

/  I 


C-OH 

XC6H4-NH-CH-CH2-CHOH-CH< 

S 

s 

C6H4-NH-CH-CH2-CHOH-CH- 

Lucius' s  Green. 


130  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

CH  = 


C-OH 

C6H4-N-CII-CH3-CHOH-CH3 

S 
C6H4-N-CH-CH2-CHOH-CH3 

Usebe's  Green. 

Of  course,  the  products  obtained  from  rosaniline  contain  one 
methyl-group  more  than  is  expressed  in  the  above  formulae  :  its 
position  can  only  be  a  matter  of  speculation. 

Aldehyde  green  is  a  basic  dyestuff,  and  was  largely  used  before 
the  introduction  of  iodine  green.  The  zinc  double  salt  came  into 
commerce  as  a  paste,  or  the  green  was  prepared  by  the  consumers. 
The  tannate,  obtained  by  precipitating  the  solution  with  tannic 
acid,  was  used  in  printing,  being  used  with  acetic  acid  and  fixed 
by  steaming. 

Diphenylnaphthylmethane  Dyestuffs  [1]. 

Certain  derivatives  of  diphenylnaphthylmethane  similar  to  the 
diphenylm  ethane  derivatives  already  described  are  in  use  as  dye- 
stuffs. 

Compounds  of  this  class  are  obtained  by  the  action  of  substi- 
tuted naphthylamines  on  tetramethyldiamidobenzophenone  in  pre- 
sence of  dehydrating  agents.  In  place  of  the  latter  compound  its 
chloride  or  the  corresponding  benzhydrol  may  be  used. 

Victoria  Blue  B  is  the  product  of  the  action  of  phenyl-a-naph- 
thylamine  on  tetramethyldiamidobenzophenone  in  presence  of 
phosphorus  oxychloride.  The  reaction  is  expressed  by  the  follow- 
ing equation  :  — 

H 


H2O. 

The  constitution  of  the  dyestuff  is  represented  by  the  formula 

(CH3)2—  N-C6H4Xr    C10H6—  NHC6H6 

(CH3)2—  N—  C6H/(  _J\C1 

Victoria   Blue   4   R.  —  This  dyestuff  is  obtained  by  a  -similar 
process  with  methylphenyl-a-naphthylamine.     Its  constitution  is 


TRIPHENYLMETHANE  DYESTUFFS.  131 

expressed  by  one  of  the  following  formulas,,  the  second  being  the 
more  probable,,  as  it  differs  greatly  in  shade  from  Victoria  Blue  B. 

(CH3)2— N-C6H4X  7C6H5 

I.  ;C— C10H6N-CH3 

(CH3)3-N-C6H/  | _J  \C1 

(CH3)2-N-C6H4  /CIOHT 

II. 


Cl 

Night  Blue  is  obtained  from  paratolyl-a-haphthylamine 
(  p-C7H7NHC10H7)  and  tetramethyldiamidobenzophenone.  These 
dyestuffs  come  into  commerce  as  hydrochlorides.  They  are 
beautiful  blue  dyestuffs,  easily  soluble,  and  dye  cotton  prepared 
with  tannic  acid  similarly  to  methylene  blue,  but  unfortunately 
the  shades  produced  are  not  very  fast  to  light.  In  general  their 
reactions  resemble  those  of  the  rosaniline  dyestuffs.  Alkalies 
precipitate  a  reddish-brown  base,  and  acids  turn  the  blue  colour 
to  yellow. 

Victoria  blue  B  base  cannot  be  crystallised.  In  a  pure  state  it 
forms  a  brick-red  powder  ;  M.P.  95°. 

Victoria  blue  4  B,  base  has  also  not  been  obtained  in  a  crystal- 
lised state.  It  resembles  the  above  in  appearance,  and  melts  at  77° 
[72]. 

B.   ROSOLIC  ACID  DYESTUFFS. 

These  dyestuffs  are  closely  related  to  those  obtained  from  ros- 
aniline, and  may  be  regarded  as  rosanilines  in  which  the  nitrogen 
is  replaced  by  a  group  containing  oxygen. 

The  actual  dyestuffs,  like  rosaniline  salts,  are  anhydrides  of  a 
carbinol.  For  example,  aurin,  C19H14O3,  is  the  anhydride  of  an 
unknown  carbinol,  trioxytriphenylcarbinol  :  — 


HO 

The  compounds  of  these  series  have  jan  acid  character,  and  in 
the  free  state  are  yellow,  while  the  salts  dissolve  in  water  with  a 
red  colour.  They  cannot  be  fixed  on  textile  fibres,  and  are  con- 
sequently almost  useless  in  dyeing.  Some  of  the  colour-lakes 
are  used  in  paper  manufacture  and  for  colouring  tapestry. 

E  V 


132  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


Aurin,  Pararosolic  Acid  [12]. 
(HO-C6H4)2=C-C6H40. 

Aurin  is  prepared  by  heating  phenol  with  oxalic  acid  and 
sulphuric  acid :  6  parts  of  phenol,  3  parts  sulphuric  acid,  and 
4  parts  of  dried  oxalic  acid  are  heated  for  about  twenty-four  hours 
to  120°-130°. 

The  melt  is  extracted  with  water,  and  the  residue  dissolved  in 
hot  alcohol,  and  ammonia  gas  passed  into  the  solution.  The 
precipitate  which  forms  is  boiled  with  acetic  acid  or  hydrochloric 
acid  [44,  48,  49].  Aurin  is  also  formed  by  condensation  of 
phenol  with  formic  acid  and  zinc  chloride  [45],  by  boiling  the 
diazo-compound  from  pararosaniline  with  water  [12],  by  heating 
dioxybenzophenone  chloride  with  phenol  [46],  and  by  action  of 
salicylic  aldehyde  on  phenol  in  presence  of  concentrated  sulphuric 
acid  [47]. 

Aurin  forms  dark  red  rhombic  crystals  or  red  needles  with 
a  green  metallic  reflex.  It  decomposes  without  melting.  It 
dissolves  in  alcohol  and  glacial  acetic  acid  with  a  yellowish-red 
colour,  and  in  alkalies  with  a  magenta-red  colour.  It  forms 
soluble  double  compounds  with  bisulphites  of  the  alkalies. 

KHSO3,C19H14O3  forms  colourless  leaflets,  immediately  decom- 
posed by  acids.  Aurin  further  forms  a  very  unstable  compound 
with  hydrochloric  acid.  Reducing  agents  convert  aurin  to 
leucaurin  (C19H16O3)  (trioxytriphenyl methane) .  On  heating  with 
aqueous  ammonia  to  120°  it  yields  pararosaniline  [13] . 

It  is  decomposed  by  heating  with  water,  phenol  and  dioxy- 
benzophenone being  produced. 

For  bye-products  of  aurin  manufacture  see  the  original 
article  [49]. 

Eosolic  Acid. 

OHC6H4  \^ 

C2oH16O3  =  OH  \Q  jj  /C — C6H4. 
CH/  \/ 

This  body  is  formed  on  boiling  the  hexazo-compound  of  rosa- 
niline  (CaoH19N3)  with  water  [50],  and  may  be  obtained  by 


TRIPHENYLMETHANE  DYESTUFFS.  133 

heating  a  mixture  of  phenol  and  cresol  with  arsenic  acid  and 
sulphuric  acid  [49] . 

The  rosolic  acid  described  by  Runge  (1834)  as  obtained  from 
the  residue  of  crude  phenol  distillation  is  probably  identical  with 
the  body  at  present  under  consideration. 

Rosolic  acid  forms  infusible  lustrous  green  crystals.  It  is 
almost  insoluble  in  water,  but  dissolves  easily  in  alcohol  and 
acetic  acid  with  an  orange-red  colour.  Its  alkaline  solutions  are 
red.  It  gives  colourless  double  compounds  with  bisulphites,  and 
in  its  general  behaviour  closely  resembles  aurin.  On  reduc- 
tion, leucorosolic  acid  (trioxydiphenyltolylmethane),  C20H1803,  is 
formed.  Dioxyphenyltolylketon  and  phenol  are  products  of  its 
decomposition  with  water  [31]. 

Two  other  products  obtained  from  aurin  have  also  been  used 
to  some  extent  in  practice. 

Red  coralline  [52]  or  Peonine  is  obtained  by  heating  crude 
aurin  with  ammonia  under  pressure,  and!  is  probably  intermediate 
in  composition  between  aurin  and  pararosaniline.  Azulin  is 
obtained  by  action  of  aniline  on  aurin,  and  is  probably  an  aurin 
containing  aniline  groups  [53] .  This  blue  dyestuff  was  largely 
used  before  the  introduction  of  aniline  blue. 


Pittacal  (Eupittonic  Acid). 

The  formation  of  this  dyestuff  was  first  observed  by  Reichen- 
bach  in  1835.  He  obtained  it  by  treating  certain  fractions  of 
beech-tar  creosote  with  baryta-water  in  presence  of  air  [54] . 

The  formation  of  similar  blue  products  has  also  been  noticed  by 
Graetzel,  and  the  subject  has  been  investigated  by  Liebermann  and 
by  A.  W.  Hofmann. 

Liebermann  gave  to  his  product  the  name  Eupitton  or  Eupittonic 
acid,  but  it  is  not  certain  that  this  body  is  identical  with  Reichen- 
bach's  Pittacal  [55].  The  constitution  and  method  of  formation 
of  this  body  were  determined  by  Hofmann  [56] . 

Eupittonic  Acid,  Hexamethoxylaurin  [55]. 

C19H8(OCH3)603. 

This  compound  is  obtained  by  action  of  carbon  hexachloride  on 
an  alkaline  solution  of  two  molecules  of  pyrogalloldiraethyl  ether 


134  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

and  one  molecule  of  methylpyrogalloldimethyl  ether  at  160°-170°. 
It  is  also  formed  by  action  of  air  on  an  alkaline  solution  of  both 
ethers  [56]. 

Eupittonic  acid  forms  orange-yellow  needles,  insoluble  in  water 
and  soluble  in  alcohol  and  ether.  It  is  a  dibasic  acid  and 
ibrms  salts  which  have  a  blue  colour  in  solution.  They  may  be 
precipitated  by  an  excess  of  alkali.  The  salts  of  the  heavy  metals 
are  sparingly  soluble  blue  lakes.  Like  aurin,  eupittonic  acid 
gives  unstable  compounds  with  acids. 

Dimethyl  ether  [56],  C25H24O9(CH3)2,  is  formed  by  action  of 
methyl  iodide  on  the  sodium  salt.  It  forms  golden-yellow  needles. 
M.P.  242°. 

Diethyl  ether  [56],  C25H24O9(C2H5)2.    M.P.  202°. 

Diacetate  [56],  C25H24O9(C2H3O)2,  yellow  needles.     M.P.  265°. 

An  analogous  compound  to  eupittonic  acid  is  obtained  by  oxi- 
dation of  pyrogalloldi methyl  ether  with  methylpyrogalloldimethyl 
ether — Tetraoxyethyldioxymethylaurin  [56] , 

C19H8(OCH3)2(OC2H5)403. 
This  compound  forms  brick-red  needles,  soluble  in  ether, 

Hexamethoxylpararosaniline  [25], 
C25H31N307 = C19H13  (OC  H3)  6N30, 

is  obtained  by  heating  eupittonic  acid  with  aqueous  ammonia 
under  pressure  to  160°-170°.  The  formation  of  this  body  is 
analogous  to  that  of  pararosaniline  from  aurin.  The  base  forms 
hair-like  colourless  needles,  which  rapidly  become  blue  on 
exposure  to  the  air.  It  is  decomposed  on  heating  with  water, 
eupittonic  acid  being  regenerated,  while  ammonia  splits  off. 

The  monoacid  salts  of  this  base  are  blue  and  the  triacid  yellow. 
The  dyestuffs  of  this  class  are  not  of  any  technical  value. 

Aurintrwarbonic  Acid  (CHROME-VIOLET)  [73]. 

/C6H3(OH)COOH 
C-C6H3(OH)COOH 


This  compound  is  obtamednSyoxidation  of  salicylic  acid  and 
methyl  alcohol  in  concentrated  sulphuric  acid  solution  with  sodium 
nitrite.  It  forms  a  red  powder  with  greenish  reflex,  and  produces 


TRIPHENYLMETHANE  DYESTUFFS.  135 

bright  shades  on  metallic  mordants.  The  chromium  lake  is  fast 
to  soap.  For  the  methyl  alcohol  may  be  substituted  formaldehyde 
or  methylal,  and  homologous  derivatives  may  be  obtained  by 
replacing  the  whole  or  molecular  portions  of  the  salicylic  acid  by 
/3-cresotic  acid. 


DYESTUFFS  FROM  BENZOTRICHLORIDE  AND  PHENOLS. 

Benzotrichloride,  according  to  Doebner  [57],  acts  on  phenols 
in  a  similar  manner  to  dimethylaniline.  The  dyestuffs  formed 
are  related  to  rosolic  acid  in  their  constitution ;  they  are  deriva- 
tives of  triphenylmethane  and  contain  an  oxygen  atom  linked  to 
the  methane- carbon  atom  and  one  benzene  ring.  Throughout, 
however,  they  contain  one  intact  phenyl  ring,  the  other  two 
containing  oxygen.  The  simplest  member  of  the  class  is  formed  by 
interaction  of  two  molecules  of  phenol  and  one  molecule  of  benzo- 
trichloride,  and  is  called  Benzaurin.  Benzaurin  stands  in  the 
same  relation  to  dioxytriphenylmethane  as  aurin  does  to  trioxytri- 
phenylmethane.  Its  constitution  is  accordingly  the  following  : — 

P  TT      p/C6H4HO. 
°6±±5     ,\C6H4— Q 

I .: I 

Benzaurin  forms  hard  lustrous  crusts.  It  is  insoluble  in  water, 
soluble  in  alcohol,  ether,  and  glacial  acetic  acid,  with  a  yellow 
colour.  It  dissolves  in  alkalies  with  a  violet  colour,  and  is  pre- 
cipitated from  its  alkaline  solution  by  acids.  It  forms  soluble 
double  compounds  with  bisulphites. 

Benzaurin  dyes  wool  and  silk  yellow  from  an  acid  bath.  It 
yields  dioxytriphenylmethane  on  reduction.  This  compound 
crystallises  from  alcohol  in  yellowish  needles. 

Resorcinbenzem,  C19H14O4,  is  an  analogous  body  obtained  by 
action  of  benzotrichloride  on  resorcin.  With  bromine  it  gives  a 
tetrabrom-compound,  which  dyes  silk  a  shade  similar  to  that 
produced  by  eosine. 

Basic  derivatives  of  the  above  bodies  have  been  recently  de- 
scribed by  Heumann  and  Rey  [74] . 

These  bodies,  called  Kosamines,  are  obtained  by  action  of  benzo- 
trichloride on  mono-  or  dialkyl  derivatives  of  metamidophenol. 
The  new  bodies  are  beautiful  red  to  violet  dyestuffs. 

One  of  the  simplest  members  of  the  series — tetramethylrosa- 


136  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

mine — is  prepared  by  heating  one  molecule  benzotrichloride  with 
two  molecules  dimethylmetamidophenol  in  benzene  solution,  or 
mixed  with  sand,  to  about  60°. 

The  hydrochloride  forms  needles  with  a  steely -blue  reflex,  and 
dissolves  easily  in  water  with  a  beautiful  bluish-red  colour ;  the 
solution  exhibits  a  bright  yellowish-red  fluorescence.  Its  consti- 
tution is  expressed  by  the  formula — 


Tetramethylrosamine  dyes  wool  and  silk  in  an  acid  bath,  pro- 
ducing shades  from  pink  to  dark  bluish  red. 

The  oxalate  forms  dark  green  needles  and  the  nitrate  steel-blue 
needles. 

By  heating  oxalic  acid  with  resorcin  and  sulphuric  acid,  Baeyer 
obtained  a  yellow  dyestuff,  which  is  probably  Euxanthone  [58] . 
According  to  Glaus  and  Andrese  [59]  it  possesses  the  formula 
C13H8O4,  while  Gukassianz  obtained  two  bodies  in  the  same 
reaction,  to  both  of  which  he  ascribes  the  formula  C14H8O5  [60] . 
Kosicki  [61]  obtained  a  dyestuff  by  heating  resorcin  with 
isosuccinic  acid  and  sulphuric  acid.  This  body,  Resorcin-isosuc- 
cinem,  has  the  same  composition  as  Brasilei'n,  C16H14O5,  and  is 
similar  in  its  properties. 


C.  PHTHALEINS   [62]. 

The  phthalei'ns  are  derivatives  of  triphenylmethane,  and  form  a 
group  of  dyestuffs  which  are  sharply  denned  from  the  rosaniline 
and  rosolic  acid  derivatives  already  described.  In  the  latter  the 
chromophorous  groups  are  in  para  positions,  while  in  the  former 
two  adjacent  positions  are  taken  up. 

The  chromophor  of  the  phthalems  is  the  lacton  ring  : — 

II 

~~C\ 
— CO/ 


TRIPHENYLMETHANE  DYESTUFFS.  137 

which  occupies  two  adjacent  positions  in  one  benzene  ring,  one 
carbon  atom  being  linked  to  another  benzene  ring. 

With  respect  to  the  colour-giving  group,  there  is  a  certain 
analogy  between  these  dyestuffs  and  those  of  the  Indigo  series, 
these  latter  being  characterised  by  the  lactam  or  lactim  ring  :  — 

C—  CO  C-COH 

/  or 

-NH  -N 


The  phthalems  are  all  derivatives  of  phthalophenone,  the  inner 
anhydride  of  triphenylcarbinolcarbonic  acid  : 


C6H5/    \C6H4COOH          C6H/ 

Triphenylcarbinolcarbonic  acid.  Phthalophenone. 

This  acid  is  not  capable  of  existing  in  a  free  state,  but  may  be 
obtained  in  form  of  its  salts.  The  relationship  between  phthalo- 
phenone and  triphenylmethane  is  easily  determined.  By  treatment 
with  alkalies  it  yields  triphenylcarbinolcarbonic  acid,  and  this  may 
be  converted  to  triphenylmethanecarbonic  acid  by  reduction  with 
zinc  powder.  On  heating  this  latter  compound,  carbon  dioxide 
splits  off,  forming  triphenylmethane. 

Phthalophenone  is  not  a  dyestuff,  the  tinctorial  character  only 
becoming  apparent  on  introduction  of  hydroxyl  groups  into  both 
phenyl  groups. 

The  phthalems  (hydroxylated  phthalophenones)  are  almost  ex- 
clusively obtained  by  action  of  phenols  on  phthalic  anhydride. 

The  position  of  the  hydroxyl  groups  with  reference  to  the 
methane  carbon  atom  has  considerable  influence  on  the  character 
of  the  dyestuff  produced.  With  simple  phenols,  as,  for  example, 
in  the  formation  of  phenolphthalem,  the  hydroxyl  group  is  in  the 
para  position  to  the  carbon  atom. 

Compounds  of  this  class  are  mostly  of  little  character  as  dye- 
stuffs.  They  are  colourless  and  only  form  coloured  salts.  Real 
dyestuffs  are  only  obtained  from  phenols  which  contain  two 
hydroxyl  groups  in  the  meta  position,  such  as  resorcin  and  pyro- 
gallol.  Probably  here  also  the  condensation  takes  place  in  a 
para  position  to  one  hydroxyl  group,  and  is  therefore  ortho  to  the 


138  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

other.  The  condensation  is  generally  attended  by  the  formation 
of  an  anhydride  between  two  hydroxyl  groups. 

The  phthale'ins,  with  exception  of  rhodamine,  are  acid  dye- 
stuffs. 

The  chromophor  of  the  phthalems  is  of  a  strong  acid  character, 
and  thus  intensifies  the  acidity  of  the  hydroxyl  groups,  and  this 
effect  may  be  considerably  increased  by  introduction  of  halogens 
or  nitro-groups  into  the  benzene  rings.  The  halogens  exert  con- 
siderable influence  on  the  shade  of  the  dyestuffs. 

The  coloured  phthalems  are  converted  into  colourless  phthalins 
on  reduction,  these  latter  bodies  being  the  corresponding  deri- 
vatives of  triphenylmethanecarbonic  acid. 


.- 

C6H/    '\C6H/  2  ~  C6H/     \C6H4COOH. 

On  treating  with  energetic  dehydrating  agents,  most  phthalems 
are  converted  into  anthraquinone  derivatives,  one  molecule  of 
phenol  being  split  off  during  the  reaction  [62]  . 

The  phthaleins  are  very  numerous,  and  only  those  of  value 
from  a  technical  or  theoretical  point  of  view  are  considered 
here. 


Phenolphthale'in  [62].     Dioxyphthalophenone, 

(OHC6H4)2=C— Ox 

CO. 
C6H4/ 

This  body  is  obtained  by  action  of  phenol  on  phthalic  anhy- 
dride in  presence  of  strong  sulphuric  acid.  The  free  phthale'in 
forms  colourless  crystals,  melting  at  about  250°;  it  dissolves  in 
alkalies  with  a  red  colour,  and  is  precipitated  by  acids  as  a  white 
precipitate.  The  alkaline  solution  is  decolorised  by  excess  of  alkali. 
On  melting  with  caustic  potash,  it  yields  benzoic  acid  and  dioxy- 
benzophenone.  On  account  of  the  change  in  colour  occasioned  by 
free  alkalies  (not  carbonate  or  ammonia),  phenolphthakm  is  useful 
as  an  indicator  in  titration. 


TRIPHENYLMETHANE  DYESTUFFS.  139 


Fluoresce'in  [62,  63]. 

HO—  C6H3 

0  CO 


(Inner  anhydride  of  resorcinphthalein.) 

Fluoresce'in  is  obtained  by  heating  an  intimate  mixture  of  two 
molecules  resorcin  with  one  molecule  phthalic  anhydride  to  190°— 
200°.  The  materials  used  in  the  manufacture  should  be  as  pure 
as  possible,  as  impure  fluorescein  is  difficult  to  purify.  In  the  pure 
state  it  forms  dark  yellow  crystals,  sparingly  soluble  in  alcohol, 
more  easily  in  glacial  acetic  acid.  It  is  almost  entirely  insoluble 
in  water,  but  dissolves  in  alkalies,  forming  a  yellowish-red  solution, 
which,  when  dilute,  exhibits  a  bright  green  fluorescence.  Acids 
precipitate  it  from  the  alkaline  solution  as  a  yellow  powder. 

Corresponding  chlorofluorescei'ns  are  obtained  by  action  of  di- 
and  tetra-chlorophthalic  anhydride  on  resorcin.  These  com- 
pounds are  entirely  different  from  those  formed  by  direct  chlori- 
nation  of  fluorescein.  In  these  the  chlorine  (bromine,  or  iodine) 
always  enters  the  resorcin-rest.  The  fluoresceins  from  the 
chlorinated  phthalic  acids  serve  as  starting-points  for  a  series  of 
very  brilliant  phthalein  dyestuffs,  which  were  first  introduced  into 
the  colour-industry  by  E.  Noelting. 

The  chlorinated  fluoresceins  have  a  somewhat  redder  shade 
than  the  corresponding  fluoresceins  which  contain  no  chlorine. 

Eosin. 

On  treating  fluorescein  with  bromine,  substitution  of  the 
hydrogen  atoms  in  the  resorcin-rests  takes  place.  The  final 
result  is  that  four  hydrogen  atoms  of  the  fluorescein  are  replaced 
by  bromine,  the  product  being  tetrabromfluorescein,  C2oH8O5Br4 
[63]. 

The  latter,  and  also  the  lower  brominated  products  are  beau- 
tiful red  dyestuffs,  the  shade  being  yellower  with  less,  and  bluer 
with  more,  bromine.  Pure  tetrabromfluorescein  [63]  crystallises 
from  alcohol  in  yellowish-red  crystals,  containing  alcohol.  It  is 
almost  insoluble  in  water,  but  forms  easily  soluble  salts  with 
alkalies,  which  exhibit  a  beautiful  green  fluorescence  in  solution. 


140  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

From  the  alkaline  solution,  acids  precipitate  the  colour-acid 
as  a  yellowish-red  precipitate.  The  salts  are  only  incompletely 
decomposed  by  acetic  acid. 

The  lead,  zinc,  alumina,  &c.,  salts  are  finely  coloured  insoluble 
lakes. 

Tetrabromfluoresce'in  and  the  lower  brominated  products  come 
into  commerce  as  sodium  or  potassium  salts,  and  form  the  various 
brands  of  soluble  eosins. 

On  wool  and  silk  they  are  dyed  from  a  slightly  acid  bath  and 
produce  brilliant  shades  of  red.  Those  on  silk  are  noteworthy  for 
their  peculiar  yellowish-red  fluorescence. 

Two  of  the  four  bromine  atoms  are  contained  in  each  resorcin 
group,  and  on  melting  with  potash  eosin  splits  up  into  phthalic 
acid  and  dibromresorcin  [64].  The  bromine  may  be  removed 
by  nascent  hydrogen ;  on  reduction  with  sodium  amalgam  colour- 
less fluorescin,  C2oH14O5,  is  formed,  and  yields  fluorescein  on 
oxidation.  Various  methods  have  been  proposed  for  the  bromina- 
tion  of  fluorescem  on  a  large  scale.  For  example,  an  alkaline 
fluorescein  solution  is  mixed  with  the  calculated  amount  of 
bromine  dissolved  in  alkali,  and  on  adding  acid  the  fluorescein 
and  bromine  are  liberated  simultaneously  and  combination  is  thus 
effected.  This  process  does  not,  however,  appear  to  be  successful, 
and  at  present  bromination  is  carried  out  in  alcoholic  solution. 
Fluorescein  in  a  finely  divided  state  is  suspended  in  alcohol,  and 
the  requisite  amount  of  bromine  added,  the  mixture  being  care- 
fully cooled.  The  hydrobromic  acid  developed  during  the 
reaction  is  utilised  by  addition  of  potassium  chlorate,  which  again 
liberates  the  bromine.  In  this  manner  a  saving  of  bromine  is 
effected,  and  only  four  atoms  are  necessary,  while  under  ordinary 
conditions  eight  atoms  are  required,  four  being  lost  as  hydro- 
bromic acid. 

Ethers  of  Eosins  [63]. 

By  treating  the  potassium  salt  of  eosin  with  methyl  iodide  or 
chloride,  or  with  ethyl  bromide,  monomethyl-  and  monoethyl- 
ethers  of  eosin  may  be  obtained,  and  these  even  surpass  the  eosins 
in  brilliancy  of  shade,  their  tone  being  in  general  somewhat  bluer. 

They  are  monobasic  acids,  as  one  unaltered  hydroxyl  group  is 
present.  The  salts  are  insoluble  in  water  and  absolute  alcohol, 
but  dissolve  with  tolerable  ease  in  alcohol  of  50  per  cent.  The 
solutions  show  a  magnificent  fluorescence. 


TRIPHENYLMETHANE  DYESTUFFS.  141 

The  potassium  salt  of  monoethyltetrabromfluorescem, 


forms  large  ruby-red  crystals  with  a  fine  green  reflex. 

The  ethyl  ether,  in  form  of  its  sodium  or  potassium  salt,  is 
extensively  used  in  silk-dyeing  as  spirit  eosin  or  "  primerose  a 
Falcool/'  For  use,  the  commercial  product  is  dissolved  in 
spirit  and  gradually  added  to  the  dye-bath,  which  is  acidified  with 
acetic  acid. 

Colourless  ethers  of  eosin  also  exist,  and  may  be  prepared  by 
heating  the  silver  salt  of  eosin  with  alcoholic  iodides  [63]. 


Iodine  Derivatives  of  Fluoresce'in. 

The  commercial  products  known  as  "  erythrosin "  are  iodine 
derivatives  of  fluorescein  corresponding  to  eosins.  The  alkali- 
salts,  which  are  the  commercial  products,  are  soluble  in  water,  and 
possess  a  much  bluer  tone  than  the  corresponding  eosins,  and 
their  solutions  do  not  exhibit  the  fluorescence  characteristic  of 
the  latter  bodies. 

The  commercial  brands  of  erythrosin  are  of  various  marks, 
according  to  the  amount  of  iodine  they  contain.  On  cotton  they 
may  be  fixed  in  form  of  an  insoluble  alumina  lake,  and  on  this 
account  are  used  somewhat  extensively  in  cotton-dyeing,  and  also 
to  a  certain  extent  in  colouring  paper. 


Dinitrodibrowftuoresce'in. 
C20H8Br2(N02)205  [62]. 

This  dyestuiF  is  formed  by  bromination  of  dinitrofluorescei'n  or 
by  nitration  of  di-  or  tetrabromfluoresce'm.  On  a  large  scale  it 
is  prepared  by  treating  dibromfluorescem  with  nitric  acid  in 
alcoholic  solution.  Pure  dinitrodibromfluorescem  forms  yellow 
needles,  sparingly  soluble  in  alcohol  and  acetic  acid.  It  is  a 
strong  dibasic  acid,  and  forms  easily  soluble  salts  with  alkalies. 
The  solutions  of  its  salts  are  yellow  if  concentrated,  red  if  dilute, 
and  do  not  fluoresce. 

The  sodium  salt  is  known  in  commerce  as  Eosin  Scarlet, 
Safrosin,  or  Lutecienne. 


142  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

It  produces  a  beautiful  bluish-red  shade  on  wool,  and  may  be 
used  in  conjunction  with  yellow  dyestuffs,  giving  fine  scarlet 
tones.  Its  application  in  wool-dyeing  has  fallen  off  considerably 
since  the  introduction  of  the  red  azo-dyes. 


Tetrabromdichlorfluoresce'in. 
C20H6Cl2Br505. 

Tetrabromtetraclilorftuoresce'in. 
C2oH4Cl4Br4O6. 

These  bodies  are  prepared  in  a  similar  manner  to  the  cosines, 
by  bromination  of  the  di-  and  tetra-chlorfluorescei'n.  The  soluble 
alkali-salts  of  these  acids  are  brought  into  commerce  as  the  various 
brands  of  Phloxin. 

Their  ethyl  ethers,  which,  like  those  of  eosin,  are  soluble  in 
dilute  alcohol,  are  known  commercially  as  Cyanosin.  Iodine 
derivatives  of  di-  and  tetra-chlorfluorescein  form  the  principal 
constituents  of  the  dyestuff  known  as  Rose  Bengal. 

The  fluorescei'n  derivatives  containing  chlorine  are  much  bluer 
in  shade  than  the  corresponding  derivatives  of  ordinary  fluorescei'n. 
Their  principal  application  is  in  silk-dyeing.  Rose  Bengal  pre- 
pared from  tetrachlorphthalic  acid  is  the  bluest  of  these  dyestuffis, 
while  Phloxin  from  dichlorphthalic  acid  is  the  yellowest. 

Here  again  the  shade  may  be  varied  at  will  by  introduction  of 
more  or  less  iodine  or  bromine. 

Rhodamine  [75]. 

The  phthaleins  of  metamidophenol  and  its  derivatives  have  been 
introduced  into  commerce  under  the  above  name.  These  dye- 
stuffs  are  characterised  by  the  brilliancy  of  the  shades  which  they 
are  capable  of  producing,  in  fact  excelling  in  beauty  all  other  red 
dyestuffs. 

Commercial  rhodamine  consists  principally  of  the  phthale'in  of 
diethylmetamidophenol.  The  condensation  of  metamidophenol 
(and  its  derivatives)  with  phthalic  anhydride  only  takes  place  in 
presence  of  strong  sulphuric  acid. 

Rhodamines  may  also  be  prepared  by  action  of  dimethyl-  or 
diethylamine  on  the  chloride  formed  on  treating  fluorescem  with 
phosphorus  oxychloride. 


TRIPHENYLMETHANE  DYESTUFFS.  143 

The  constitution  of  the  simplest  rhodamine  is  probably 
analogous  to  that  of  fluorescem,  and  is  expressed  by  the 
formula  :  — 

H2NC6H3          C6H4 

o<    >c<r    \co. 

H2NC6H3        X0X 

Unlike  the  ordinary  phthalems,  rhodamine  possesses  basic  and 
acid  properties.  It  forms  soluble  salts,,  from  which  the  base  is 
not  separated  by  alkalies.  The  solutions  are  turned  yellow  by  an 
excess  of  mineral  acid. 

The  shade  of  rhodamine  is  a  magnificent  red,  and  exhibits  on 
silk  a  hitherto  unrivalled  fluorescence. 

More  recently  the  condensation-product  of  succinic  acid  and 
dimethylmetamidophenol  has  been  prepared  on  a  large  scale  and 
sold  as  fUiodamine  S.  It  is  especially  adapted  for  cotton-dyeing. 

Pyronines  [76]. 

The  Pyronines  are  a  series  of  red  basic  dyestuffs  of  comparatively 
recent  introduction.  They  are  derivatives  of  dipheny  1m  ethane, 
and  resemble  the  rhodamines  in  shade.  A  typical  pyronine  may  be 
prepared  as  follows  :  —  Dimethylmetamidophenol  is  condensed 
with  formaldehyde,  and  the  resulting  dioxytetramethyldiamido- 
diphenylmethane  is  treated  with  strong  sulphuric  acid,  whereby 
one  molecule  of  water  is  split  off,  and  a  leuco-base,  tetramethyl- 
diamidodiphenylmethane-oxide,  is  formed,  according  to  the  equa- 
tion :  — 


C6H3-N(CH3)2 
CH,/  =  H20+CH2<        >0 

C'H*<N(CH3)2  C6H3-N(CH3)2. 

From  this  the  dyestuff  (Pyronine   G)  is  obtained  by  oxidation. 
It  has  the  formula  :  — 


CH< 


C6H3-N(CH3)2 

>Q 
C6H3—  N(CH8)aCl. 

I 


Pyronine  B  is  the  corresponding  ethyl  derivative. 
The    pyronines   yield    brilliant   bluish-red   shades   on   cotton 
mordanted  with  tannic  acid. 


144  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Gallem  and  Ccerule'in  [65]. 

Gallem. — The  first  product  of  the  interaction  of  phthalic 
anhydride  and  pyrogallol  is  a  phthalem  anhydride  analogous  to 
fluoresce'in,  which,  however,  undergoes  further  oxidation  by  the 
air,  two  hydroxyl  groups  being  converted  to  quinone  groups.  The 
gallem  thus  formed  possesses  the  formula — 


It  differs  from  fluorescei'n  in  containing  two  quinone  oxygen 
atoms  in  combination  with  two  benzene  rings. 

Gallem  is  generally  prepared  by  heating  phthalic  anhydride 
with  gallic  acid  to  200°.  The  latter  is  converted  into  pyrogallol 
at  this  temperature,  carbonic  acid  being  split  off. 

In  the  pure  state  gallem  forms  brilliant  green  crystals  or  a 
brownish-red  powder,  easily  soluble  in  alcohol  with  a  dark  red 
colour,  and  difficultly  soluble  in  ether. 

The  salts  with  the  alkalies,  lime,  and  baryta  are  soluble  in 
water  with  a  red  colour,  which  is  turned  blue  by  an  excess  of 
alkali.  On  reduction,  it  is  converted  to  hydrogallem  and,  finally, 
to  gallin.  It  forms  greyish-violet  lakes  with  alumina  and 
chromic  oxide.  It  produces  a  fine  violet  on  wool  mordanted  with 
bichromate. 

In  printing  it  is  applied  with  acetate  of  aluminium  or  chromium 
and  steamed,  whereby  acetic  acid  is  liberated,  and  the  aluminium 
or  chromium  lake  of  gallem  is  fixed  on  the  fibre. 

Coerule'in  [65],  C20H8O6,  is  formed  by  heating  gallein  with 
twenty  times  its  weight  of  concentrated  sulphuric  acid  to  200°. 
The  dyestuff  is  precipitated  by  water,  and  in  this  state  forms  a 
bluish-black  powder,  which  takes  a  metallic  lustre  on  rubbing. 
It  is  almost  insoluble  in  water,  alcohol,  and  ether,  slightly  soluble 
in  glacial  acetic  acid  with  a  green  colour,  and  easily  in  concen- 
trated sulphuric  acid  with  an  olive-green  colour.  It  forms  a  blue 
solution  with  hot  aniline. 


TRIPHENYLMETHANE  DYESTUFFS.  145 

It  crystallises  from  hot  concentrated  sulphuric  acid  in  warty 
crystals.  Reducing-agents  convert  it  to  reddish-brown  coerulin, 
C20H12O6.  On  warming  with  acetic  anhydride,  a  triacetylcoerulein, 
C2oH9O6(C2H3O)3,  is  formed.  Coerulein  forms  colourless  soluble 
compounds  with  bisulphites;  these  compounds  being  easily 
decomposed  by  boiling  or  by  action  of  alkalies  or  acids.  In 
dyeing  and  printing  the  bisulphite  compound  is  generally  used. 
For  printing,  the  coerulein  bisulphite  compound  (Coerulein  S)  is 
mixed  with  aluminium  or  chromium  acetate,  printed,  and  steamed. 
This  decomposes  the  acetate  and  the  bisulphite  compound  simul- 
taneously, and  coerulein  becomes  fixed  as  aluminium  or  chromium 
lake.  Wool  is  previously  mordanted  with  bichromate  and  tartar. 

The  shades  produced  are  dark  green,  not  very  bright,  but 
useful  on  account  of  their  great  fastness. 

On  distilling  with  zinc  powder,  coerulein  gives  phenylanthra- 
cene,  and,  according  to  Buchka,  is  a  derivative  of  phenyloxan- 
thranol : — 

OH 
I 


CO 

The   constitution   of  coerulein  is  expressed   by  the   following 
formula  : — 

CO  OH 


CTT  /  \n  Tjr_ r\ 

6^4  \  /^n 

[66]. 


O- ^C.H, 


.0 


Glycere'ins  [67]. 

Reichl  gives  this  name  to  a  series  of  coloured  products  obtained 
by  action  of  phenols  on  glycerin  in  presence  of  concentrated 
sulphuric  acid.  The  quantity  of  dyestuff  formed  is,  however, 
so  small  that  one  can  scarcely  formulate  any  reaction  in  form 
of  an  equation. 

Similar  bodies  to  these  from  glycerin  are  also  obtained  from 
many  organic  acids,  alcohols,  and  sugars. 


146 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


CHAPTER  VI. 

QUINONEBIIDE    DYESTUFFS. 

THE  dyestuffs  comprised  under  this  Lead  are  derivatives  of  the 
hitherto  unknown  imido-compounds  of  the  quinones,  and  include, 
amongst  others,  the  Indarnines  and  Indophenols. 

By  replacing  the  oxygen  atoms  of  quiiione  by  the  divalent 
group  NH,  the  following  compounds  are  obtained,  according  as  the 
substitution  takes  place  once  or  twice. 


and 


NH 


These  compounds  are  unknown  in  the  free  state.  Various 
derivatives  are,  however,  known,  amongst  the  simplest  of  which 
may  be  mentioned  quinonechlorimide  and  quinonedichlordiimide. 


Quinonechlorimide.        Quinonedichlordiiraide. 


QUINONEIMIDE  DYESTUFFS.  1-17 

The  above-mentioned  indamines  and  indophenols  must  be 
regarded  as  more  complex  derivatives  of  the  quinoneimides. 

These  dyestuffs  are  formed  by  oxidation  of  a  paradiamine  in 
presence  of  a  monamine  or  a  phenol,  or  by  action  of  quinonedi- 
chlordiimide  on  the  latter. 

In  the  oxidation  process,,  as,  for  example,  that  of  parapheny- 
lenediamine  with  aniline,  the  former  is  probably  converted  into 
quinonediimide  HN=C6H4=NH,  which,  on  further  oxidation 
attacks  the  benzene  chain  of  the  aniline,  and  enters  in  the  para 
position  to  the  amido- group.  The  indamiiie  produced  has  the 
constitution  [1]  : 

N 


This  constitutional  formula  is  deduced  from  the  following 
facts : — On  reduction  the  compound  takes  up  two  atoms  of 
hydrogen,  forming  paradiamidodiphenylamine  : — 

H2N— C6H4—NH— C6H4— NH2. 

As  the  indamine  may  be  reproduced  on  oxidation,  this  body 
must  be  regarded  as  the  leuco-base  of  the  dyestuff.  That  the 
nitrogen  atom  effecting  the  linkage  in  the  indamine  is  tertiary 
is  seen  from  the  fact  that  a  paradiamine  substituted  in  both 
amido-groups,  as,  for  example,  diethylparapheiiylenediamine, 

C2H5— HN— C6H4— NH— C2H5, 

is  incapable  of  forming  an  indamine.  That  the  nitrogen  atom 
effecting  the  linkage  in  the  indamines  occupies  the  para  position  to 
the  amido-group  is  easily  proved,  as  paradiamines  do  not  react  with 
para  substituted  monamines,  or  at  least  only  in  a  different  manner. 
Para-diamines  substituted  in  one  amido-group  react  like  primary 
amines,  and  the  monamine  may  also  be  secondary  or  tertiary.  In 
many  such  cases  the  formation  of  an  ammonium-chloride  group 

L2 


148 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


Cl 

(«N(CH8)2) 

has  to  be  assumed. 

The  behaviour  of  certain  tertiary  indamines  shows  that  their 
production  is  attended  by  an  intermediate  formation  ofaquinone- 
imide.  If,  on  the  one  hand,  paraphenylenediamine  is  oxidised 
with  diaiethylaniline,  and,  on  the  other,  unsymmetrical  dimethyl- 
paraphenylenediamine  [(CH3)2NC6H4NH2]  with  aniline,  indamines 
are  formed  in  both  cases,  but  are  not  identical  with  each  other, 
but  isomeric,  as  by  further  action  of  aniline  they  yield  two 
different  dimethylsaffranines. 

This  behaviour  is  easily  explained  under  the  following 
assumptions  : — Paraphenylenediamine  yields  first  the  body 
HN — C6H4 — NH;  while  from  dimethylphenylenediaraine  the 
chlormethylate,  C1(CH3)2N— C6Ht— NH,  is  produced.  The 
further  action  of  these  compounds  on  the  respective  monamines 
must  necessarily  produce  different  indamines,  the  constitution  of 
which  is  expressed  by  the  following  formula  : — 


II  Cl  I 

]ST(CET3)       Nil, 

It  is  not  improbable  that  the  red  dyestuff  obtained  by  Wurstcr 
by  oxidation  of  dimethylparaphenylenediamine  is  none  other  than 
the  chlormethylate  of  methylquinoneimide  : — 

C1(CH3)2=N=C6H4NH. 

This  compound  yields  dimethylphenylenediamme  on  reduction, 
and  reacts  with  monamines  and  phenols  to  produce  indamines 
and  indophenols. 

The  indophenols  are  related  to  the  analogues  of  oxyamidodi- 
phenylamine  in  the  same  manner  as  the  indamines  are  todiamido- 
diphenylamine. 


QUIXONEIMIDE  DYESTUFFS.  149 

The  formation  of  dyestuffs  by  oxidation  of  paradiamines  with 
monamines  was  first  discovered  by  R.  Nietzki  [48]  in  1879,  who 
later  [1]  determined  the  constitution  of  the  iridammes.  Witt, 
in  1879,  discovered  the  reaction  between  nitrosodimethylaniline 
and  amines  and  phenols. 

Bernthsen  [36]  showed  later  that  certain  dyestuffs  containing 
sulphur  (methylene  blue  and  Lauth's  violet)  also  belong  to  this 
class  of  colouring- matters. 


1.  IND  AMINES. 

Indamine  (PHENYLENE  BLUE)  [l].j 
H2N—  C6H4^ 


This  compound  is  formed  by  oxidation  of  p-diamidodiphenyl- 
amine,  or  of  a  mixture  of  equal  molecules  of  paraphenylenediamine 
and  aniline.  It  is  the  simplest  member  of  the  indamine  series, 
and  its  salts  are  greenish  blue  and  are  mostly  soluble  in  water. 
Acids  turn  the  solutions  green,  and  rapid  decomposition,  with 
formation  of  quinone,  sets  in.  The  iodide  separates  in  long 
brilliant  green  crystals  from  a  mixture  of  the  hydrochloride  and 
potassium  iodide.  Indamine,  on  reduction,  yields  paradiamido- 
diphenylamine.  On  heating  with  a  solution  of  an  aniline-salt, 
phenosaffranine  is  formed. 

Tetrametliylindamine  [1,  2,  3], 

(BINDSCHEDLER'S  GREEN.) 

(CH3)2N—  C6H4^  ^ 


This  compound  is  obtained  by  oxidation  of  equal  molecules  of 
dimethylparaphenylenediamine  and  dimethylaniline  [1,  2,  3]. 
The  solutions  of  the  salts  have  a  fine  green  colour,  which  is  turned 


150  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

blue  by  alkalies.    If  the  action  of  the  latter  is  protracted,  dimethyl- 
amine  is  evolved,,  and  probably  an  indophenol 

(CH3)2N—C6H4Vx 


is  formed.  This  indamine  is  in  general  more  stable  than  the 
former  one,  but  is  decomposed  on  warming  with  acids,  quinone 
and  dimethylaniline  being  formed. 

It  yields  tetramethyldiamidodiphenylamine  [1]  on  reduction. 

Iodide,  C16H20N3I  [1],  is  formed  on  addition  of  potassium 
iodide  to  a  solution  of  the  hydrochloride  or  zinc  double  salt,  and 
separates  in  long  green  needles.  It  is  pretty  soluble  in  pure 
water,  but  insoluble  in  a  solution  of  potassium  iodide. 

Zinc  double  salt  [2,  3],  (C16H20N3Cl)2,ZnCl2,  forms  coppery 
needles,  which  are  easily  soluble  in  water. 

Mercury  double  salt,  (C16H20N3Cl)2,HgCl2. 

Platinum  double  salt,  C16H20N3C)2,PtCl4. 

Toluylene  Blue  [1,  4]. 
Cl 

I 
(CH3)2=NC6H5 

> 

HNCH—  NH 


Toluylene  blue  may  be  obtained  by  mixing  solutions  of 
equivalent  quantities  of  nitrosodimethylaniline  hydrochloride  and 
metatoluylenediamine,  and  also  by  oxidation  of  the  latter  base 
with  dimethylparaphenylenediamine.  It  is  an  amido-indamine 
characterised  by  a  greater  degree  of  stability  than  the  previous 
ones.  The  monoacid  salts  are  blue,  and  the  diacid  salts  are 
colourless. 

The  hydrochloride,  C15H12N4,HC1,  forms  soluble  needles  which 
possess  a  coppery  lustre. 

On  reduction,  toluylene  blue  gives  triamidotolylphenylamine. 
On  heating,  toluylene  red  [4]  (see  Azine  Dyestuffs)  is  formed. 

The  red  dyestuff  obtained  by  Wurster  by  oxidation  of  dimethyl- 
paraphenylenediamine is  probably  closely  related  to  the  inda- 
mines  [5].  According  to  Wurster  and  Sendtner,  this  compound 


QUIXONEIMIDE  DYESTUFFS.  151 

corresponds  to  a  base  of  the  formula  C8H10N2.  It  possesses  the 
remarkable  property  of  reacting  with  amines  and  phenols  to  pro- 
duce ind  amines  and  indophenols  respectively.  It  is  possible  that 
this  compound  is  a  methylate  of  methylquinone-diimide  of  the 
constitution  — 

Cl 


3\^jp    _  TT     _  TV/TTT 

CH  /       «  —    4  — 

Tetramethylparaphenylenediamine      gives     a     blue      dyestuff, 
C10H14N2,  on  oxidation. 


2.  INDOPHENOLS   [7,  8,  12]. 

This  series  of  dyestuffs,  which  were  first  prepared  by  Witt  and 
Koechlin,  by  simultaneous  oxidation  of  paradiamines  or  para- 
amidophenols  with  phenols,  exhibit,  both  as  regards  constitution 
and  general  behaviour,  a  close  relationship  to  the  indamines. 
Like  the  latter,  they  are  decomposed  by  acids  with  formation  of  a 
quinone.  In  general  they  possess  a  weak  basic  nature,  but, 
unlike  the  indamines,  form  colourless  salts,  and  have  mostly  a  blue 
or  violet  colour  in  the  free  state. 

On  reduction  they  yield  analogues  of  paraniido-oxydiphenyl- 
amine. 

Indophenols  may  be  obtained  by  oxidation  of  paradiamines  with 
phenols,  or  by  action  of  nitrosodimethylaniline  or  quinonechlor- 
imide  on  the  latter  class  of  compounds. 

According  to  the  above  remarks  the  constitution  of  the  simplest 
indophenol  (from  paraphenylenediamine  and  phenol)  should  be 
expressed  by  the  formula, 

HN=C6H4=N— C6H4— OH  ; 

but  the  properties  of  the  compounds  of  this  class  agree  better 
with  the  formula — 

0=C6H4=N—  C6H4— NH2. 

For  example,  the  indophenols  do  not  possess  acid  properties, 
as  might  be  expected  if  an  hydroxyl  group  were  present;  on  the 
contrary,  they  are  weak  bases. 

The  leuco-compounds,  however,  possess  decided  phenolic  pro- 
perties. They  are  soluble  in  alkalies,  but  oxidise  extremely 


152  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

readily  in  the  air,  iiidophenols  being  formed,  which,  being 
insoluble  in  alkalies,  separate  out.  In  presence  of  acid  the  leuco- 
indophenols  are  stable  in  the  air. 

The  application  of  these  dyestuffs  in  dyeing  and  printing  is 
based  on  the  above  properties  of  the  leuco-compouuds.  The 
process  is  similar  to  indigo  vat-dyeing.  The  goods  are  impreg- 
nated with  an  alkaline  solution  of  the  leuco-compound,  the  colour 
being  developed  by  oxidation  in  the  air,  or  by  passing  through  a 
bath  of  potassium  bichromate.  Indophenol  may  also  be  produced 
directly  on  the  fibre,  a  mixture  of  the  diamine  and  phenol  being 
applied,  and  the  dyestuff  developed  by  passing  through  bichromate 
or  bleaching-powder  solution. 

Only  the  indophenols  from  dimethylparaphenylenediamine  and 
a-naphthol  and  phenol  have  been  found  capable  of  technical 
application. 

The  former  compound  is  of  an  indigo-blue  colour,  and 
crystallises  from  benzene  in  brilliant  green  needles.  It  forms  a 
colourless  solution  with  acids ;  an  excess  decomposes  it  with 
formation  of  a-naphthaquinone  and  dimethylparaphenylene- 
diamine [12].  The  dyestuff  from  phenol  is  greenish  blue. 

The  manufacture  of  the  indophenols  is  effected  by  oxidation  of 
an  alkaline  solution  of  the  reacting  compounds  with  sodium  hypo- 
chlorite,  or  with  air  in  presence  of  copper  oxide.  An  interesting 
method  of  obtaining  indophenol  is  by  the  action  of  dibrom-a- 
naphthol  on  dimethylparaphenylenediamine. 

The  indophenols  are  very  fast  to  soap  and  light ;  their  great 
sensitiveness  towards  acids  and  certain  difficulties  encountered  in 
their  application,  however,  render  them  unable  to  compete  with 
indigo.  Indophenol,  however,  appears  to  be  of  use  when  combined 
with  indigo,  i.e.  when  a  vat  of  the  mixed  dyestuffs  is  used.  It  is 
claimed  that  this  mixed  vat  is  more  economical  than  the  simple  indigo 
vat,  while  the  fastness  and  beauty  of  the  shades  are  not  affected. 

A  trichlorindophenol, 

HN-CH 

has  been  obtained  by  Schmitt  and  Andresen  [10]  by  action  of 
trichlorquinonechlorimide  on  dimethylaniline.  It  forms  beautiful 
green  needles. 

Dyestuffs  may  also  be  produced  by  action  of  quinonechlorimide 
and  of  nitrosophenol  on  phenols  in  alkaline  solution.  They  are, 


QUINONEIMIDE  DYESTUFFS.  153 

however,  very  unstable,  and  probably  contain  an  bydroxyl  group 
in  place  of  the  amido-group  in  the  previously  described  indo- 
phenols.  The  simplest  of  these  compounds  would  possess  the 
formula :—  HOC6H4 


3.  INDAMINES  AND  INDOPHENOLS  CONTAINING 
SULPHUR. 

(THIAZINES.) 

This  class  comprises  a  series  of  dyestuffs  corresponding  to  the 
indamines  and  indophenols,  but  which  contain  one  atom  of  sulphur 
in  their  molecule.  This  sulphur  atom  effects  a  linkage  between 
two  benzene  rings,  and  the  indamines  of  this  series  stand  in  the 
same  relationship  to  thiodiphenylamine, 


as  the  common  indamines  do  to  diphenylamine.  The  sulphur  atom 
enters  the  two  benzene  chains  in  the  ortho  position  to  the  imido- 
group,  and  accordingly  thiodiphenylamine  may  be  regarded  as 
containing  three  rings  each  containing  six  members.  This  is  ex- 
emplified by  the  following  formula  [36] : — 

H  H 

^C       S       C 

HC^    c     c    XCH 

I      II    II 

HC        C       C        CH 

H      H      H 

The  amido  and  hydroxyl  derivatives  of  thiodiphenylamine  are, 
like  those  of  diphenylamine,  leuco-compounds. 
There  is  an  erroneous  impression  that  the  group 

S 


154  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

acts  as  chromophor,  and  that  tliiodiphenylamine  is  the  chromogen 
of  this  class  of  dyestuffs.  From  Bernthsen's  constitutional  for- 
mulae, however,  these  bodies  belong  to  the  Indamine  group,  and 
their  chromophor  must  be  the  paraquinonediimide  group — 

N— 


This  is  evident  from  the  fact  that  the  amido  derivatives  of 
thiodiphenylamine  are  not  dyestuffs,  but  leueo-compounds.  The 
presence  of  the  sulphur  atom  serves  to  give  greater  stability 
to  the  molecule,  and  these  bodies  are  stable  to  acids. 

In  general,  the  whole  character  of  the  series  is  considerably 
modified. 

The  simplest  indarnine, 

/CeH, 


corresponds  to  Lauth's  Violet : 

C6H3-NH2 

<        >S 


In  this  series  also  the  nitrogenous  groups  are  generally  in  the 
para  position  to  each  other. 

The  sulphuretted  indamines  may  be  produced  by  introduction  of 
amido  groups  into  thiodiphenylamine,  and  oxidation  of  the  result- 
ing leuco-com pounds.  They  are  generally  prepared,  however,  by 
a  peculiar  reaction  discovered  by  Lauth  [14].  If  a  paradiamine  is 
oxidised  in  presence  of  sulphuretted  hydrogen  in  acid  solution, 
one  atom  of  nitrogen  splits  off  as  ammonia,  and  two  molecules  of 
the  diamine  combine,  one  atom  of  sulphur  entering  into  both  rests 
simultaneously.  The  resulting  body  is  an  indamine  containing 
sulphur.  These  compounds  are  also  formed  on  oxidation  of  thio 


QUIXONEIMIDE  DYESTUFFS.  155 

derivatives  of  paradiamines.  Small  quantities  are  further  obtained 
by  oxidation  of  amidodiphenyl amines  in  presence  of  sulphuretted 
hydrogen. 

These  dyestuffs  are  far  more  stable  than  the  indamines  and 
indophenols,  and,  unlike  these,  do  not  give  quinone  when  treated 
with  acid.  For  this  reason  they  are  capable  of  practical  applica- 
tion, one  of  them,,  methylene  blue,  discovered  by  Caro,  being  used 
on  a  very  large  scale.  The  dyestuffs  of  this  class  have  a  violet  or 
blue  shade. 


LautKs  Violet  (Thionine)  [14,  36]. 

/C6H3—  N=HO 

>s 


is  formed  by  oxidation  of  paraphenylenediamine  hydrochloride 
in  presence  of  sulphuretted  hydrogen,  by  fusing  paraphenylene- 
diamine with  sulphur  and  oxidising  the  resulting  compound,  and 
finally  by  oxidation  of  paradiamidothiodiphenylamine. 

The  base,  C12H9N3S,  forms  a  black  crystalline  powder  or  needles 
with  a  greenish  reflex.  It  dissolves  in  alcohol,  forming  a  reddish- 
violet  solution,  and  in  ether,  forming  an  orange  solution. 

Hydrochloride,  C12H9N3S,HC1,  forms  beetle-green  needles,  so- 
luble in  water  with  a  violet  colour. 

Hydriodide,  C12H9N3S,HI,  is  sparingly  soluble  in  water  [36]. 

Lauth/s  Violet  gives  a  green  solution  with  concentrated  sulphuric 
acid,  and  on  dilution  the  colour  changes  through  blue  to  violet. 
On  reduction  it  yields  paradiamidothiodiphenylamine  [36]  . 

Isothionine  is  an  isomerie  dyestuff  formed  by  oxidation  of  a 
diamidothiodiphenylamine  of  unknown  constitution  [36]  . 


Methylene  Slue  [13,  15,  16,  36,  53]. 
N7        3>S 


This  dyestuff  was  discovered  by  Caro,  who  obtained  it  by  oxida- 


156  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

tion  of  dimethylparaphenylenediamine  in  presence  of  sulphuretted 
hydrogen. 

The  dimethylparaphenylenediamine  used  in  this  and  other  pro- 
cesses is  prepared  by  reduction  of  nitrosodimethylaniline,  obtained 
by  action  of  nitrous  acid  on  dimethylaniline. 

Carols  process  was  formerly  used  on  an  industrial  scale.  A  con- 
siderable improvement  was  effected  by  oxidising  equivalent  quan- 
tities of  dimethylparaphenylenediamine  and  dimethylaniline  in 
presence  of  thiosulphuric  acid.  The  most  recent  processes  have 
for  their  starting-point  dimethylparaphenylenediamine-thiosul- 
phonicacid:  xN(CH3)v[l] 

C6H3-S  .  S03H  [3J 
W 


This  compound  is  obtained  by  oxidation  of  dimethylparapheny- 
lenediamine in  presence  of  sodium  hyposulphite,  or  by  action  of 
hyposulphurous  acid  (thiosulphuric  acid,  H2S2O3)  on  the  red  oxi- 
dation product  of  dimethylparaphenylenediamine.  Two  processes 
may  be  employed  for  the  manufacture  of  methylene  blue  from  this 
compound.  (1)  The  thiosulphonic  acid  is  oxidised  with  dimethyl- 
aniline,  whereby  an  insoluble  compound  : 

N(GH,)9 

S—  S03  , 
C0H4N(CH3)3 

tetramethylindamine-thiosulphonate,  is  formed.  On  boiling  with 
zinc-chloride  solution,  it  yields  sulphuric  acid  and  leucomethylene 
blue,  which  is  converted  into  the  dyestuff  on  oxidation.  (2)  On 
reduction,  the  thiosulphonic  acid  yields  dimethylparaphenylene- 
diamine mercaptan  —  ^  N(CH  )0  [1] 

C6H3-SH         3[3] 
[4] 


or,  on  treating  with  acids,  the  corresponding  disulphide  (C8HnN2S)2. 
On  oxidation  with  dimethylauiline,  both  these  compounds  give  the 
same  soluble  green  indamine  : 


,.-»! 

I 

tetramethylindamine  sulphide,  which  is    transformed    to  leuco- 


L 


QUINONKIMIDE  DYESTUFFS. 

methylene  blue  and  methylene  blue  on  standing  or  on  warming 
the  solution.  Small  quantities  of  methylene  blue  are  formed  by 
oxidation  of  tetramethyldiamidodiphenylamine  in  presence  of  sul- 
phuretted hydrogen,  and  by  treating  tetramethyliiidamine  with 
sulphuretted  hydrogen. 

Another  method  used  in  the  manufacture  of  the  so-called  ethy- 
lene  blue  consists  in  treating  nitrosodimethylaniline  in  sulphuric 
acid  solution  (sp.  gr.  1*4)  with  zinc  sulphide.  Leuco-methylene 
blue  is  produced,  and  yields  the  dyes  tuff  on  oxidation. 

It  is  certain  that  methylene  blue  is  the  tetramethyl  derivative 
of  Lauth's  violet,  although  it  cannot  be  obtained  by  direct  methyl- 
ation  of  the  latter.  Its  constitution  is  analogous  to  that  of  tetra- 
methylindamine.  Like  this,  it  contains  a  pentavalent  nitrogen 
atom,  which  is  in  combination  with  two  methyl  groups  and  an 
hydroxyl  or  acid  radical.  The  hydrochloride  has  the  constitution 
expressed  at  the  head  of  the  section.  The  properties  of  the  base 
of  methylene  blue  are  those  of  an  ammonium  base,  and  this  agrees 
with  the  above  conception  of  its  constitution.  The  base  is  not 
easily  separated  from  its  salts.  'It  is  best  obtained  by  decom- 
position of  the  hydrochloride  with  silver  oxide,  and  has  probably 
the  formula  C16H18N3SOH.  It  dissolves  easily  in  water  with  a 
blue  colour. 

Hydrochloride,  C16H18N3SCL,  forms  small  lustrous  leaflets, 
easily  soluble  in  water. 

Zinc  double  salt,  2(C16H18N3SC1)  +  ZnCl3  +  H3O  (commercial 
methylene  blue),  forms  coppery  needles,  easily  soluble  in  water, 
sparingly  soluble  in  zinc  chloride  solution. 

Hydriodide,  C16H18N3SI,  forms  lustrous  brown  needles,  sparingly 
soluble  in  water. 

Concentrated  sulphuric  acid  dissolves  methylene  blue  with  a 
green  colour.  Reducing  agents  convert  it  to  its  leuco-derivative, 
tetramethyldiamidothiodiphenylamine — 

/C6H3-N=(CH3)2 
NH  >S 

XC6H3-N=(CH3)2 

This  base  forms  colourless  leaflets,  which  oxidise  in  the  air  to 
methylene  blue.  On  treating  with  methyl  iodide,  the  dimethyl- 
iodide  of  pentamethyldiamidothiodiphenylamine — 


158  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

/C6H:!-N(CH3)2 
CH3-N       >S 
is  formed.  XC6H3-N(CH3)S 

As  this  compound  is  also  formed  by  metliylation  of  the  leuco- 
compound  of  Lauth's  violet,  the  relationship  between  the  two  dye- 
stuffs  is  demonstrated. 

Like  most  ammonium  bases,  methylene  blue  does  not  dye  wool 
easily,  but  is  readily  fixed  on  silk  and  tannined  cotton.  It  has 
also  a  slight  affinity  for  un mordanted  vegetable  fibres.  Methylene 
blue  is  principally  used  in  cotton-dyeing.  It  dyes  a  greenish 
shade  of  blue,  which  shows  a  dull  tone  similar  to  that  of  indigo. 
It  is  very  fast  to  light,  and  tlie  shades  may  be  readily  modified  by 
other  basic  dyestufts,  such  as  methyl  violet  or  malachite-green. 

An  analogous  dyestuff  to  methylene  blue  is  obtained  from  mono- 
ethylparaphenylenediamine  [Oehler,  20],  and  another  from  meth- 
oxydimethylparaphenylenediamine  [Miilhauser,  21]. 


ImidotModiphenylimide  [36]. 

^CQH4 

N  >S 

^C6H3=NH 

This  body  contains  one  amido  group  less  than  Lauth's  violet, 
and  is  formed  by  oxidation  of  monamidothiodiphenylamine. 

The  base  forms  small  reddish -brown  needles,  soluble  in  alcohol 
and  ether  with  the  same  colour. 

Hydrochloride,  C1oH8N2S,HCl  +  liH2O,  forms  a  brown  preci- 
pitate insoluble  in  ether.  It  dissolves  in  water  with  blue-violet 
colour,  and  gives  a  green  solution  with  concentrated  sulphuric 
acid.  The  zinc-chloride  double  salt,  (C12H8N2S5HCl)2ZriCl2,  forms 
long  brownish-violet  needles. 

The  compounds  hitherto  described  correspond  to  the  indamines ; 
the  following  ones  must  be  regarded  as  sulphuretted  indophenols, 
as  oxygen  partly  takes  the  place  of  the  nitrogenous  groups  of  the 
former. 

The  influence  of  the  sulphur  atom  in  adding  to  the  stability  of 
the  molecule  is  also  very  apparent  in  these  bodies,  as  they  exhibit 
a  far  greater  resistance  to  the  action  of  chemical  agents  than  the 
corresponding  simple  indophenols. 


QUINONEIM1DE  DYESTUFFS.  159 

Thionoline  (Thioxindophenol)  [36]. 

/  C6H3— ] 

N  >S 


C6H— NH 


This  compound  may  be  obtained  by  oxidation  of  paramidophenol 
in  presence  of  sulphuretted  hydrogen,  or  by  treating  Lauth's  violet 
with  an  alkali.  In  the  latter  case  the  imido-group  is  eliminated 
as  ammonia. 

The  base  forms  yellowish-brown  leaflets,  with  a  green  reflex ; 
the  hydrochloride  crystallises  in  fine  black  needles,  forming  a 
reddish-violet  solution  with  water. 

The  dimethyl  derivative  of  thionoline  (Methylene  Violet)  is 
formed  by  boiling  methylene  blue  with  alkali,  methylene  azure,  the 
sulphone  of  methylene  blue,  C16H17N3SO2,  being  simultaneously 
produced  [36]. 

The  base  of  dimethyl  thionoline,  CUH13SN3O,  forms  long  needles, 
and  its  alcoholic  solution  shows  a  reddish-brown  fluorescence. 

The  hydrochloride  crystallises  in  brilliant  green  needles  which 
dissolve  in  concentrated  sulphuric  acid  with  a  green  colour,  and 
dyes  silk  violet. 

Oxythiodiphenylimide  [36], 


is  produced  by  oxidation  of  oxythiodiphenylamine  (from  oxy- 
diphenylamine  and  sulphur).  It  forms  reddish-brown  needles 
which  dissolve  sparingly  in  ether,  acetone,  &c.,  with  an  orange-red 
colour. 

Thionol  (Dioocytlnodiphenylimide)  [36], 

N  x      '  >  S  , 
is  formed,  along  with  thionoline.  by  boiling  Lauth's  violet  with 


160  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

alkali  or  dilute  sulphuric  acid,  and  also  by  treating  thiodiphenyl- 
amine  with  sulphuric  acid  containing  75  per  cent.  SO3.  It  is 
insoluble  in  water  and  crystallises  from  hydrochloric  acid  in 
needles,  which  contain  hydrochloric  acid.  It  possesses  simultane- 
ously weak  basic  and  strong  acid  properties. 

The  acid  solutions  are  reddish  violet,  the  alkaline  solutions 
violet  in  colour. 

The  barium  salt,  Cl3H7NSO.,BaO,  forms  brilliant  green  leaflets 
soluble  in  water. 


Metlnjlene  Red  [19,  36,  53]. 


This  compound  is  a  bye-product  in  the  preparation  of  methylene 
blue  by  the  old  process.  Its  formation  is  greatest  in  presence  of 
a  large  amount  of  sulphuretted  hydrogen. 

Its  constitution  is  expressed  by  the  formula 

/N(CH3)2C1 

C6H3-N 

\     >S 

\s/ 

This  is  deduced  from  the  following  properties.    On  reduction  it 

/N(CH3)2[4] 

yields  dimethylparaphenylenediamine-mercaptanC6H3—  NH2       [1] 

XSH          [2] 
and  is  decolorised   by  alkalies,  the  corresponding    thiosulphonic 

/N(CH3)3 
acid,  C6H0—  NH0         ,  being  formed  amongst  other  compounds. 

XS-SO3H 

The  hydrochloride,  C8H9N2S2,HC1,  is  easily  soluble  in  water, 
and  is  extracted  from  the  solution  by  phenol.  The  hydriodide  is 
more  sparingly  soluble  and  crystallises  from  water  in  thick  prisms. 
On  reduction,  and  subsequent  oxidation  with  dimethylaniline, 
methylene  blue  is  formed. 


QUINONEIMIDE  DYESTUFFS.  161 

Methylene  Green. 

This  compound  is  obtained  by  treating  methylene  blue  with 
nitrous  acid.  It  dyes  textile  fibres  a  fine  dark  green  colour,  and 
appears,  from  its  properties,  to  be  a  nitro-derivative  of  methylene 
blue.  In  its  behaviour  towards  fibres  it  resembles  j;he  latter. 


4.  OXYINDAMINES  AND  OXYINDOPHENOLS. 
(OXAZINES.) 

This  denomination  includes  a  series  of  compounds  analogous  to 
the  thioindamines  and  containing  an  oxygen  atom  in  place  of  the 
sulphur  atom  of  the  latter. 

These  compounds  are  formed  by  the  action  of  iiitrosodimethyl- 
aniline  or  of  quinonedichlorimide  on  certain  phenols  or  phenol- 
carbonic  acids  in  a  hot  alcoholic  or  acetic  acid  solution,  or  by 
oxidation  of  these  phenols  with  paradiamines  at  a  medium  tem- 
perature. 

The  dyestuffs  from  /3-naphthol  and  from  gallic  acid  are  best 
known.  The  former  was  discovered  almost  simultaneously  by 
Witt  and  Meldola. 

Naphthol  Blue  [29,  51]. 

N 
C18H15N2O.C1     =     C1.N(CH3)2  =  C6H3^  C10H6. 


This  dyestuff  is  best  prepared  by  heating  nitrosodimethylaniline 
hydrochloride  with.  /3-naphthol  in  alcoholic  solution.  A  part  of 
the  nitrosodimethylaniline  becomes  reduced  to  dimethylparapheny- 
lenediamine  during  the  reaction. 

The  base  is  soluble  in  benzene  with  a  red  colour. 

The  hydrochloride,  C18HUN2O,HC1,  and  the  zinc  chloride 
double  salt  form  bronzy  needles,  which  form  blue-violet  solutions 
with  water. 

Platinum  double  salt,  (C18H14N2O,HCl)2PtCl4. 

The  compound  dyes  on  cotton  prepared  with  tannic  acid,  and 
produces  a  somewhat  dull  violet-blue  shade  similar  to  indigo.  The 
dyestuff  is  known  commercially  as  Fast  Blue,  Naphthol  Blue,  and 

M 


162  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Meldola's  Blue.    The  dyestuff  exerts  an  extremely  irritating  action 
on  the  mucous  membrane  of  the  nostrils. 

/3-naphthol  reacts  with  chlorquinonediimide,  producing  a  red 
dyestuff  of  the  composition  C16H10N2O  [51] .  It  does  not  form  a 
diazo-compound,  and  therefore  probably  contains  no  free  amido- 
group.  Its  constitution  is  probably  expressed  by  the  formula — 


NH 

The  base  has  a  yellow  colour  without  fluorescence,  the  salts 
dissolve  in  concentrated  sulphuric  acid  with  a  green  colour,  which 
on  dilution  turns  through  blue  to  red. 

Under  similar  conditions  a-naphthol  yields  a  dyestuff  which 
dissolves  in  dilute  hydrochloric  acid  with  a  red  colour,  and  pro- 
duces a  greyish-violet  shade  in  dyeing. 

Resorcin  reacts  with  nitrosodimethylaniline,  producing  a  fluo- 
rescent violet  dyestuff  [29]  . 

Sulphonic  acids  of  this  series  may  also  be  obtained  from 
sulphonic  acids  of  the  phenols. 

Muscarine. 
C18H15N202C1. 

This  dyestuff  is  an  hydroxyl  derivative  of  naphthol  blue,  and  is 
obtained  by  interaction  of  nitrosodimethylaniline  hydrochloride 
and  a  dioxynaphthalene,  M.P.  186°.  Its  constitution  is  repre- 
sented by  the  formula  :  — 

^\ 
C1N(CH3)2C6H3C          C10H5OH. 


The  base  is  yellowish  brown,  and  is  obtained  by  precipitating 
the  violet  solution  of  one  of  the  salts  with  an  alkali.  It  forms  a 
bluish-green  solution  with  concentrated  sulphuric  acid,  and  on 
dilution  the  colour  changes  through  blue  to  violet,  a  violet  pre- 
cipitate being  formed  finally.  It  dyes  a  dull  blue  shade  on  cotton 
mordanted  with  tannic  acid. 


QUINONEIMIDE  DYESTUFFS.  163 

Nile  Blue. 

(C18H16N30)2S04. 

This  dyestuff  is  prepared  by  heating  a-naphthylamine  hydro- 
chloride  with  nitrosodimethylmetamidophenol  hydrochloride  in 
acetic-acid  solution  to  100°.  Nile  blue  is  soluble  in  water  and 
alcohol  with  a  blue  colour.  Alkalies  produce  a  brownish  pre- 
cipitate, soluble  in  ether  with  a  brown  fluorescence.  Sulphuric 
acid  dissolves  it  with  a  yellow  colour,  which  on  dilution  changes 
through  green  to  blue.  On  adding  hydrochloric  acid  to  an 
aqueous  solution  of  Nile  blue,  the  sparingly  soluble  hydrochloride 
is  precipitated. 

The  hydrochloride  has  the  constitution  expressed  by  the  formula  : 


Cl  .  NCH     =  CH<  CHNH. 


10 


Nile  blue  dyes  on  cotton  prepared  with  tannic  acid  and 
tartar  emetic,  producing  a  greenish-blue  shade  of  great  beauty  and 
purity,  similar  to  methylene  blue,  but  clearer. 

Gallocyanine  [32,  51]. 

This  dyestuff  has  attained  considerable  importance,  especially 
in  calico-printing,  and  is  obtained  by  acting  with  nitrosodime- 
thylaniline  hydrochloride  on  gallic  acid  in  a  hot  alcoholic  or 
acetic  acid  solution.  The  compound  crystallises  out  in  brilliant 
green  needles.  The  mother-liquors  always  contain  dimethyl- 
paraphenylenediamine. 

Gallocyanine  is  sparingly  soluble  in  hot  water,  alcohol,  and 
acetic  acid.  The  solutions  have  a  violet  colour.  It  possesses 
simultaneously  acid  and  basic  properties,  and  is  precipitated  from 
the  reddish- violet  alkaline  solution  by  acids. 

Gallocyanine  dissolves  with  difficulty  in  hydrochloric  acid, 
forming  a  reddish- violet  solution.  Its  solution  in  strbng  sulphuric 
acid  is  blue. 

It  forms  an  almost  colourless  crystalline  compound  with  sodium 
bisulphate. 

The  composition  of  gallocyanine  is  expressed  by  the  formula — 

C15H12N206; 

MS 


164  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

and  its  formation  is  explained  by  the  following  equation  : — 
3C8H10N20  +  2C7HG05  =   2C15H12N205   +   C8H12N2  +   H2O. 


-Nitrosodimetliyl- 
aniline. 


Gallic 
acid. 


Gallocyaniue. 


Dimetliyl- 

paraphenyl- 

dianiine. 


Water. 


Gallocyanine  is  easily  soluble  in  hot  aniline,  and,  on  cooling,  an 
anilide  crystallises  in  long  green  needles.  This  anilide  is  formed 
by  action  of  two  molecules  of  aniline,  according  to  the  equation  — 

C15H12N205  +  2C6H5NH3  =  C27H24N4O4  +  H2O. 

This  compound  may  be  regarded  as  an  aniline  addition-product 
of  the  anilide  — 

5    [51]. 


The  anilide  possesses  well-marked  basic  properties. 

The  methyl-ether  of  gallic  acid  reacts  with  nitrosodimethylaniline, 
producing  a  methyl-ether  of  gallocyanine,  C15HnN2O5  (CH3)  .  This 
compound  is  a  dyestuff,  and  is  known  in  commerce  as  Prune  [51]  . 

Prune  differs  from  gallocyanine  inasmuch  as  the  former  is  a 
base  forming  stable  soluble  salts,  while  in  gallocyanine  the  acid 
properties  are  predominant. 

Nitrosodimethylaniline  reacts  also  with  the  amide  of  gallic 
acid  ("  gallaminic  acid  "),  and  forms  a  blue  dyestuff,  which  is  met 
with  in  commerce  in  form  of  its  bisulphite  compound  under  the 
name  Gallamine  Blue. 

Gallocyanine  is  constituted  according  to  one  of  the  following 
formulae  :  — 


HOOC 


HOOC 


N(CH3)5 


OH 


From  the  fact  that  the  methyl-ether  of  gallocyanine  yields  a 
diacetyl  derivative,  the  second  formula  appears  the  more  probable. 
The  pentatomic  nitrogen  present  is  probably  saturated  by  the 


QUINONEIMIDE  DYESTUFFS.  165 

carboxyl  group  in  gallocyanine,  or  by  an  hydroxyl  group  in 
Prune,  as  the  base  contains  no  ammonium  hydroxyl  group. 

These  three  dyestuffs  are  capable  of  dyeing  on  mordants,  and 
produce  violet  lakes  with  iron,  aluminium,  and  especially  with 
chromium  oxides.  On  account  of  the  fastness  of  the  shades  pro- 
duced, these  dyestuffs  are  largely  used  in  calico-printing  and  in 
wool-dyeing.  In  printing,  a  mixture  with  sodium  bisulphite  and 
chromium  acetate  is  used,  the  insoluble  chromium-lake  being 
produced  by  steaming.  Wool  may  be  dyed  without  any  mordant, 
but  faster  shades  are  obtained  by  chroming  the  wool  first.  Prune 
having  more  pronounced  basic  properties  may  be  dyed  on  cotton 
prepared  with  tannic  acid  and  tartar  emetic. 

Prune  comes  into  the  market  as  a  powder ;  Gallocyanine  and 
Gallamine  Blue  generally  as  pastes. 


5.  DICHROl'NES. 
Liebermann's  Phenol  Dyestuffs  [30]. 

As  it  has  been  demonstrated  that  certain  of  these  dyestuffs  are 
derivatives  of  phenoxazine,  they  are  best  described  here. 

On  treating  phenols  in  concentrated  sulphuric  acid  solution  at 
40°-50°  C.  with  nitrous  acid,  peculiar  violet  or  blue  compounds 
are  formed.  They  are  of  distinctly  acid  character,  and  are  repre- 
cipitated  from  alkaline  solutions  on  addition  of  acids.  Their 
alkaline  solutions  exhibit  a  remarkable  fluorescence,  and  for  this 
reason  this  class  of  compounds  is  also  known  as  Dichroi'nes. 

The  dyestuff  from  phenol  has  the  composition,  C18H15NO3.  It 
forms  a  brown  powder,  insoluble  in  water,  soluble  in  alkalies  with 
a  blue  colour.  The  thymol  dyestuff  has  the  formula  C3oH36N2O4, 
and  the  orcin  dyestuff  C2iH18N2O6.  Both  have  a  violet  colour. 

Eesofujin  (Weselsktfs  Diazoresorufiri). 
C12H7NO3.     [31,  33,  34,  54.] 

This  compound  is  formed  by  action  of  nitro-  or  nitrosoresorcin 
or  nitrobenzene  on  resorcin  in  presence  of  concentrated  sulphuric 
acid  at  1 70°.  It  may  also  be  obtained  from  resazurin  (see  below) 
by  various  methods.  Resazurin  yields  resorufin  on  heating  alone 


166 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


or  with  concentrated  sulphuric  acid  to  110°,  by  reduction  with 
sodium  bisulphite,  or  with  zinc  powder  or  iron,  and  subsequent 
oxidation  in  the  air.  Resorufin  is  also  formed  in  the  preparation 
of  resazurin.  The  following  synthetic  methods  give  a  clear  idea 
of  its  constitution.  On  dissolving  an  equal  number  of  molecules 
of  nitrosoresorcin  and  resorcin  in  concentrated  sulphuric  acid  a 
dyestuff  is  formed,  which,  on  heating  the  mixture  to  100°,  goes 
over  into  resorufin.  The  intermediate  product  of  the  reaction 
may  be  regarded  as  an  indophenol  of  resorcin  formed  according 
to  the  scheme  : — 


O= 


OH 


HO 


=  N  — 

OH  II 

OH 


On  heating  to  100°,  another  molecule  cf  water  is  eliminated, 
thus  :— 


and   the    resulting    resorufin   has 
expressed  by  the  formula  — 


accordingly    the   constitution 


Resorufin  is  also  formed  by  heating  nitrosophenol  or  quinone- 
chlorimide  with  resorcin,  or  by  heating  nitrosoresorcin  with  phenol 
or  by  oxidation  of  paramidophenol  with  resorcin,  or  by  oxidation 
of  asymmetrical  amidoresorcin  with  phenol.  (These  reactions  are 
all  carried  out  in  presence  of  concentrated  sulphuric  acid. 

Resorufin  forms  small  brown  needles,  insoluble  in  water, 
sparingly  soluble  in  alcohol  and  ether,  and  easily  soluble  in  hot 


QUINONEIMIDE  DYESTUFFS.  167 

concentrated  hydrochloric  acid.  It  dissolves  readily  in  alkalies, 
and  the  solution  exhibits  a  beautiful  cinnabar-red  fluorescence. 

Resorufin  ethyl-ether,  C12H6NO3(C2H5),  is  formed  by  heating  the 
silver  salt  with  ethyl  iodide  and  alcohol.  It  forms  orange-red 
needles,  M.P.  225°. 

Hydroresorufin  (Dioxyphenoxazm)  :  — 

•o\ 

tHOH. 


This  is  a  leuco-compound  formed  by  reduction  of  resorufin  in 
acid  solution.  It  forms  long  silky  needles,  M.P.  216°.  In 
alkaline  solution  it  oxidises  rapidly  to  resorufin. 

Tetrabromresorufin  is  obtained  by  action  of  bromine  on  an 
alkaline  solution  of  resorufin.  Its  sodium  salt,  C13H2Br4NO3Na 
+  2H2O,  forms  the  commercial  Resorcin  Blue  or  Fluorescent  Blue. 
It  dyes  wool  and  silk  in  an  acid  bath,  and  produces  bluish-  violet 
shades,  remarkable  for  their  beautiful  red  fluorescence. 


Eesazurin  (WeselsJcy's  Diazoresorcin] .     [31,  33,  34.] 
C12H7N04. 

This  compound  is  formed  by  action  of  nitrous  acid  on  an 
ethereal  solution  of  resorcin.  It  forms  lustrous  green  prisms, 
which  are  insoluble  in  water  and  ether,  sparingly  soluble  in 
alcohol,  and  easily  soluble  in  alkalies.  The  alkaline  solutions 
are  violet,  and  have  a  brown  fluorescence. 

The  constitution  of  resazurin  is  not  known  with  certainty.  It 
contains  one  oxygen  atom  more  than  resorufin,  and  the  two  are 
evidently  closely  related  from  the  ease  with  which  resazurin  may 
be  transformed  into  resorufin.  The  two  also  yield  the  same 
dioxyphenazoxin  on  reduction.  It  is  probable  that  resazurin  is 
expressed  by  the  formula  : — 


168  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Acetyl  resazurin,  C12H6NO4(C2H3O),  forms  long  red  needles, 
M.P.  222°. 

Resazurin  ethyl  ether,  C12H6NO4(C2H5),  forms  dark  red  needles, 
M.P.  215°. 


Orcirufin.    [33,34,  55.] 
C14HUN03. 

This  compound  is  formed  by  action  of  nitrous  acid  on  an 
ethereal  orcin  solution,  and  is  identical  with  the  dyestuff  obtained 
by  Liebermann  by  action  of  nitrous  acid  on  orcin  in  presence  of 
sulphuric  acid. 

Orcirufin  yields  a  monoacetyl  derivative,  M.P.  204°. 

Resorufamin,  Cl2H8N2O2. — This  body  is  closely  related  to  reso- 
rufin,  one  oxygen  atom  of  the  latter  being  replaced  by  an  amido- 
group.  It  is  obtained  by  heating  quinonedichlorimide  with 
resorcin  in  alcoholic  solution. 

Resorufamin  is  only  obtained  in  small  quantity.  It  is  a  base 
forming  salts  which  are  easily  soluble,  and  the  solutions  exhibit 
practically  the  same  fluorescence  as  the  alkaline  solution  of  reso- 
rufin. 

Orcirufamin,  C13H10N2O2,  is  obtained  in  a  similar  manner,  but 
is  formed  in  larger  quantity.  It  closely  resembles  the  above. 

Lacmoid. — This  colouring-matter,  which  probably  belongs  to 
the  above  series,  was  obtained  by  heating  resorcin  with  sodium 
nitrite  [46,  Traube  and  Hock].  It  forms  blue  salts  with  alkalies, 
and  their  solutions  are  turned  red  by  acids.  For  this  reason  it 
has  been  proposed  as  an  indicator  in  titration. 


AZINE  DYESTUFFS. 


169 


CHAPTER  VII. 

AZINE  DYESTUFFS. 

THIS  chapter  comprises  the  saffranines  and  their  allies,  amongst 
which  are  the  eurhodines,  toluylene  red,  the  so-called  neutral 
dyes,  Basle  blue,  and  probably  Magdala  red  and  Mauveine. 
Most  of  these  dyestuffs  have  been  long  known,  but  we  owe  most 
of  our  knowledge  of  their  constitution  to  the  researches  of 
Witt  on  the  eurhodines.  Witt  observed  that  a  compound  of 
this  class  [37],  obtained  by  action  of  a-naphthylamine  on  ortho- 
amidoazotoluene,  gives,  on  removal  of  the  amido- group,  tolunaph- 
thazine  (naphthylene-toluylenequinoxaline).  All  these  dyestuffs 
are  derivatives  of  an  azine  (quinoxaline  of  Hinsberg).  The 
simplest  body  of  the  azine  group  is  phenazine  (azophenylene  of 
Clans  and  Rasenack)  : — 


N 
The  group  '  I  \    which   replaces  two  ortho-hydrogen  atoms  in 

each  benzene  ring,  is  the  chromophor  of  the  whole  series. 

The  azine  group,  with  the  four  adjacent  carbon  atoms,  forms  a 
new  ring,  containing  six  atoms,  so  that  phenazine  may  be  regarded 
as  containing  three  rings,  like*  anthracene. 

*  c 


N. 

Phenazine. 


170 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


The  azines  are  in  some  respects  analogous  to  the  quinone- 
anilides. 

While  in  the  reaction  between  a  paraquinone  and  a  diamine, 
only  one  amido-group  enters  into  the  reaction  with  one  quinone 
group,  the  action  of  an  orthodiamine  and  an  orthoquinone 
is  just  double,  both  oxygen  atoms  being  eliminated  in  form  of 
water  with  the  hydrogen  of  the  amido-group,  the  nitrogen  of  the 
latter  entering  in  the  place  of  the  oxygen. 

The  reaction  will  be  easily  understood  from  the  following 
graphic  equation  : — 


11 


o 


0 


H 


N 


N 


R- 


11 


+  H20. 


The  simplest  azines  are  not  dyestuffs,  they  are  slightly  coloured 
bodies,  generally  yellow,  and  possessing  weak  basic  properties, 
their  salts  being  decomposed  by  water. 

The  introduction  of  amido-groups  intensifies  tlie  basic  character 
of  the  azine,  and  increases  the  dyeing  properties. 

Hydroxyl  groups  produce  colouring-matters  of  a  slightly  acid 
nature,  which  have,  however,  only  little  tinctorial  power. 

Monamidoazines  (Eurhodines)  are  only  weak  dyestuffs,  the 
dyeing-power  being  fully  developed  by  introduction  of  two  or 
more  amido-groups. 

The  azines  are  closely  related  to  the  indamines;  the  latter 
being  derivatives  of  paraquinonediimide,  while  the  former  corre- 
spond to  the  orthoquinonediimides,  only  in  this  case  the  conden- 
sation so  common  in  the  ortho  series  takes  place. 

The  relationship  between  the  two  classes  of  compounds  is  shown 
by  the  fact  that  the  indamines  may  be  easily  converted  into 
azines,  and  that  monamines,  with  a  free  para  position  capable  of 
yielding  indamines  on  oxidation,  give  azines  when  the  para 
positions  are  occupied.  The  conversion  of  indamines  into  azines 
is  especially  instructive  in  the  case  of  amidoindamines — for 


AZINE  DYESTUFFS. 


171 


example,  Toluylene  blue.  On  heating  an  aqueous  solution  of 
this  compound  for  some  time,  Toluylene  red,  an  amidoazine,  is 
formed  with  elimination  of  hydrogen.  The  hydrogen  is  not 
liberated  as  such,  but  converts  a  portion  of  the  toluylene  blue  to 
its  leuco-base  [4] . 

The  reaction  will    be  readily    understood  from  the   following 
equation : — 


(CII3)2N— 


Toluylene  blue. 


Toluylene  red. 


The  amido-group  adjacent  to  the  nitrogen  atom  linking  the 
benzene  chains  in  the  indamine,  loses  its  hydrogen  atoms,  and 
becomes  linked  to  the  second  benzene  chain,  while  the  imido- 
group  is  simultaneously  reduced  to  an  amido-group. 

If  an  oxidising  agent  is  present,  the  conversion  of  toluylene 
blue  into  leuco-base  does  not  take  place. 

The  simpler  indamines  only  yield  azines  in  presence  of  a 
primary  amine.  In  this  case  saffranines  are  formed.  These 
bodies  contain  probably  a  phenylazonium  group,  viz.,  an  azine 
group  containing  a  pentatomic  nitrogen  atom,  wrhich  is  linked 
with  chlorine  and  a  benzene  ring. 

Although  the  basic  character  of  the  azines  is  increased  by  the 
introduction  of  amido-groups,  the  azine  group  plays  the  principal 
part  in  the  formation  of  salts.  If  acetyl  groups  are  introduced 
into  the  amido-groups  the  basic  properties  of  the  compound  are 
decreased,  but  not  entirely  destroyed. 

A  further  confirmation  of  this  is  seen  in  the  behaviour  of  the 
polyacid  salts  and  of  the  corresponding  diazo-compounds. 

Diamidoazines  generally  form  three  series  of  salts,  of  which  the 
monoacid  are  red,  the  diacid  blue,  and  the  triacid  green.  The 
two  latter  compounds  are  decomposed  by  water,  the  first  one  is 
stable. 

If  a  diazo-group  is  introduced  into  a  diamidoazine  the  com- 
pound forms  stable  diacid  salts,  which  have  likewise  a  blue  colour. 
With  a  second  diazo-group  a  stable  green  salt  may  be  obtained. 


172  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

As  diazo-groups  can  only  be  formed  from  amido-groups,  and  as 
the  conversion  into  diazo-compound  increases  the  stable  salt- 
forming  capacity  once  for  each  diazo-group,  it  is  a  necessary  con- 
clusion that  the  acid  radical  present  in  the  red  stable  salt  cannot 
be  connected  with  the  amido-groups. 

Another  point  in  this  connection  is  that  the  amidoazines  dye 
fibres  the  colour  of  the  monoacid,  and  not  of  the  polyacid  salts, 
thus  showing  that  the  azine  group  effects  the  combination  with 
the  fibre. 

In  the  mon  amidoazines  both  nitrogen  atoms  appear  capable  of 
combining  with  acids,  at  least  this  is  probable  from  the  various 
colour-reactions  which  these  bodies  give  with  strong  acids. 

The  azine  dyestuffs  mostly  possess  a  well-marked  fluorescence ; 
this  appears  in  some  cases  in  the  alcoholic  solutions  of  the  salts, 
and  in  others  in  the  ethereal  solution  of  the  base. 

1.  EURHODINES  [37,  38]. 
(AMIDOAZINES.) 

This  class  of  bodies  was  discovered  by  Witt.  They  are  formed 
by  action  of  orthoamidoazo-compounds  on  monamines  (ortho- 
amidoazotoluene  on  a-naphthylamine),  by  action  of  orthoquinones 
on  triamines  with  two  adjacent  amido-groups,  and  by  action  of 
nitrosodimethylaniline  or  of  quinonedichlordiimide  on  certain 
monamines,  in  which  the  para  position  is  occupied  [50,  52] . 

The  eurhodines  are  in  general  weak  basic  dyestuffs.  The  base 
is  usually  yellow,  the  monoacid  salts  red,  and  the  diacid  salts 
green.  Both  are  readily  decomposed  by  water.  The  monoacid 
salts  dye  silk  red,  but  on  washing  a  change  to  the  yellow  colour  of 
the  base  takes  place.  Most  eurhodines  give  a  red  solution  with 
concentrated  sulphuric  acid,  the  colour  changing  through  black 
and  green  into  red  again  on  dilution.  The  ethereal  solutions  of 
the  bases  exhibit  a  yellowish-green  fluorescence. 

Eurhodine, 

C17H13N3     [37]. 
(Amidotolunaphthazine.) 

This  compound  is  obtained  by  heating  orthoamidoazotoluene 
with  a-naphthylamine  hydrochloride.      The   base  forms  golden- 


AZINE  DYESTUFFS. 


173 


yellow  needles  sparingly  soluble  in  alcohol  and  ether,  easily  in 
aniline  and  phenol.  It  sublimes  without  decomposition.  The 
ethereal  solution  shows  a  green  fluorescence.  Concentrated  sul- 
phuric acid  dissolves  it  with  a  red  colour,  which  changes  through 
black  and  green  into  red  on  dilution.  It  reacts  with  nitrous  acid 
producing  a  diazo-compound,  which  is  decomposed  on  boiling 
with  alcohol,  eurhodol  ethyl  ether,  C17HnN2  — O  — C2H5,  being 
formed. 

The  hydrochloride,  C17H13N3,HC1,  forms  deep  red,  bronzy 
needles. 

Witt  accords  the  following  constitution  to  this  eurhodine  [28]  : 


Eurhodine, 

H2N-C6H3/ 


[50]. 


(Amidophe?maphthazine.  ) 

Is  formed  by  action  of  quinonedichlordiimide  on  /3-naphthylamine 
according  to  the  following  equation  :  — 

N 

>C10H6  +  2HC1. 
N 


H 


The  base  has  a  yellow  colour,  and  fluoresces  in  ethereal  solu- 
tion.    The  salts  are  red,  without  fluorescence,  and  are  decomposed 


174  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

by  water.  The  compound  forms  a  brown  solution  with  concen- 
trated sulphuric  acid.  It  yields  naphthophenazine  on  boiling  with 
nitrous  acid  and  alcohol  :  — 


N 


Dimethy  lamidop  liennaph  thazin  e, 
(CH8)2NC6H3<^  )  \C10H6. 

is  prepared  by  action  of  nitrosodimethylaniline  on  /3-naphthyl- 
aniline  [52]. 

The  base  is  yellow,  dissolves  in  concentrated  sulphuric  acid  with 
a  violet  colour,  and  forms  blue  unstable  salts  [52]. 

• 

Amidoplienophenanthrazine. 


This  eurhodine  is  formed  by  action  of  phenanthrenequinone  on 
unsymmetrical  triamidobenzene.  The  base  forms  yellow  flocks 
or  a  brown  crystalline  powder.  The  salts  are  sparingly  soluble, 
and  of  a  carmine-red  colour.  The  reactions  are  similar  to  those 
of  the  preceding  compounds  [38]. 

Eurhodines  are  also  formed  by  the  action  of  triamidobenzene 
on  j£-naphthoquinone,  glyoxal,  benzil,  isatine,  and  leuconic  acid. 

A  dimethyl  eurhodine  (dimethylamidophenotoluazine), 


[39], 
is  formed  on  boiling  diazotised  toluylene  red  with  alcohol. 


AZINE  DYESTUFFS.  175 

2.  EURHODOLS. 
(OXYAZINES.) 

These  bodies  are  formed  by  melting  the  azinesulphonic  acids 
with  caustic  potash  [40]  and  by  heating  the  eurhodines  with 
concentrated  hydrochloric  acid  to  180°  [38]. 

They  resemble  the  eurhodines  in  colour  and  fluorescence,  and  in 
their  reactions  with  concentrated  sulphuric  acid,  but  differ  in 
possessing  both  phenolic  and  basic  properties. 

Oxynaphthoto  luazine, 
C17H12N30. 

This  eurhodol  is  obtained  by  heating  the  corresponding  eurho- 
dine,  C17H13N3,  with  hydrochloric  acid  or  dilute  sulphuric  acid. 
It  dissolves  in  concentrated  sulphuric  acid  with  a  red  colour,  and  is 
precipitated  from  this  solution  in  yellow  flocks  on  addition  of 
water  [38]. 

Eurhodol, 

C24H14N2O. 

( Oxyphenanthrenenaphthazine.) 

This  compound  is  formed  by  melting  phenanthrene-naphthazine- 
sulphonic  acid  (from  phenanthrenequinone  and  a/3-naphthylene- 
diaminesulphonic  acid)  with  caustic  potash.  It  dissolves  in  con- 
centrated sulphuric  acid  with  a  blue  colour,  which  suddenly 
changes  into  bright  red  on  dilution.  Its  sulphonic  acid  is  a 
yellow  dyestuff. 

The  colour-reactions  exhibited  by  the  eurhodols  with  acids  of 
different  concentrations  can  only  be  explained  on  the  assumption 
that  mono-  and  diacid  salts  exist,  in  which,  according  to  circum- 
stances, one  or  both  nitrogen  atoms  of  the  azine  group  exert  basic 
functions. 

3.  TOLUYLENE  RED. 

(CH3)2NC6H3<f  |  ^>C6H2/  [4] . 

•N/  NH 

Toluylene  Red  is  a  diamidoazine,  the  simplest  of  which,  diamido- 


176  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

phenazine,  is  obtained  by  oxidation  of  triamidophenylamine  with 
manganese  dioxide. 

NH 


NH2-C6H3<        \C6H4  .  NH2  +  0 
NH/ 


C6H3-NH2. 

\N/ 

Toluylene  red  is  a  dimethyl  derivative  of  a  homologue  of 
diamidophenazine,  and  is  prepared  by  oxidation  of  dimethylpara- 
phenylenediamine  with  metatoluylenediamine  at  the  boil,  and  is 
also  formed  by  heating  toluylene  blue  (amidoindamine)  [4]  (see 
introduction  to  the  Azine  Dyestuffs) .  The  base  forms  orange-red 
crystals,  which  contain  four  molecules  of  water.  The  water  may 
be  expelled  at  150°,  leaving  the  anhydrous  compound,  which  is 
of  a  blood-red  colour  [4J.  The  alcoholic  and  ethereal  solutions 
fluoresce  strongly. 

The  monoacid  hydrochloride  is  a  fine  red  dyes  tuff,  which  is 
turned  blue  by  hydrochloric  acid,  and  green  by  concentrated 
sulphuric  acid.  The  zinc-chloride  double  salt  forms  crystals  with 
a  metallic  lustre  [4] . 

Toluylene  red  comes  into  commerce  as  Neutral  Red,  and  being  a 
basic  dyestuff  is  fixed  on  cotton  by  means  of  tannic  acid. 

Toluylene  red  contains  one  free  amido-group  and  yields  a  diazo- 
compound,  which  gives  a  dimethyl  eurhodine  on  boiling  with 
alcohol  [39]. 

By  oxidation  of  paraphenylene-diamine  and  metatoluylene- 
diamine, a  non-methylated  toluylene  blue  is  formed  which  yields 
a  corresponding  toluylene  red  on  heating.  This  latter  forms 
a  tetrazo-compound  which  yields  methylphenazine  (benzene- 
tolazine)  : 

N 

C6H4<;  |  >C6H3CH3  [39], 
N 

on  boiling  with  alcohol. 

A  violet  dyestuff,  Toluylene  Violet,  to  which  Witt  ascribes  the 
formula  CUH14N4,  is  formed  by  treating  toluylene  blue  with  an 
excess  of  metatoluylenediamine  [4] .  A  similar  dyestuff,  known 
commercially  as  Neutral  Violet,  is  the  product  of  the  oxidation 
of  dimethylparaphenylenediamine  with  metaphenylenediamiue. 


AZINE  DYESTUFFS.  177 

4.  SAFFRANINES  [1,  2,  3,  4]. 

The  dyestuffs  coming  under  this  classification  contain  four 
nitrogen  atoms.  Unlike  the  previous  azine  dyestuffs,  they  contain 
at  least  three  hydrocarbon  chains.  Although  their  behaviour 
shows  them  to  be  phenazine  derivatives,,  they  differ  in  many 
respects  from  those  previously  described.  Especially  noticeable  is 
their  strong  basic  character,  which  in  many  respects  resembles 
that  of  the  quaternary  ammonium  bases,  and  the  characteristic 
bitter  taste  of  the  latter  compounds  is  also  present  in  the  saffra- 
nines.  Another  point  of  difference  from  the  rest  of  the  azine 
dyestuffs  is  that  the  free  base  has  the  same  colour  as  the  mono- 
acid  salts. 

The  well-marked  basic  properties  of  the  saffranines  are  doubt- 
less functions  of  the  azine  group,  although  two  amido-groups  are 
also  present.  The  hydrogen  atoms  of  the  latter  may  be  replaced 
by  alcohol  or  acid  radicals ;  and  from  the  fact  that  the  diacetyl 
derivatives  are  still  mono-acid  bases,  it  is  evident  that  the  strongly 
basic  properties  of  the  azine  group  remain  unaffected. 

The  saffranines  form  three  series  of  salts.  The  mono-acid  salts 
are,  like  the  base,  red  and  very  stable ;  the  diacid  salts  are  blue, 
and  the  triacid  green.  The  two  latter  series  are  decomposed  by 
water ;  and  in  fact  the  green  salts  can  only  exist  in  presence  of 
concentrated  sulphuric  or  hydrochloric  acids.  Both  amido-groups 
may  be  diazotised  [1],  The  primary  diazo-compound  forms  blue 
diacid  salts,  which  are  formed  in  slightly  acid  solutions,  and 
correspond  to  the  blue  diacid  saffranine  salts.  The  green  tetrazo- 
compounds  have  not  been  analysed,  but  probably  correspond  to 
the  triacid  salts.  The  salts  of  these  diazo-compounds  are  not 
decomposed  by  water. 

The  saffranines  are  products  of  the  following  reactions : — By 
heating  primary  monamines  with  indamines,  whereby  part  of  the 
latter  undergo  reduction  [1,  3,  4]  ;  by  oxidation  of  paradiamido- 
diphenylamine  and  its  analogues  with  primary  bases  [1]  ;  and  by 
oxidation  of  paradiamines  with  two  molecules  of  the  latter  [3,  4] . 

In  the  oxidation  of  paradiamines  with  monamines  two  different 
monamines  may  be  used,  of  which  one  only  need  be  primary. 
For  the  diamine  and  one  monamine  the  same  conditions  must  be 
observed  as  for  the  production  of  an  indamine,  *.  e.  that  the 
diamine  must  only  be  substituted  in  one  amido-group,  and  the 
monamine  must  possess  a  free  para  position.  As  an  indamine  is 

N 


I-'Q 
/O 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


always  formed  as  an  intermediate  product,  all  three  processes  may 
be  said  to  depend  on  the  same  reaction — i.  e.  an  indamine  is  formed 
either  from  diamidodiphenylamine  or  from  the  diamine  and  one 
molecule  of  monamine.  The  monamine  used  in  the  second  stage 
of  the  process  must  not  be  substituted  in  the  amido-group,  but 
the  para  position  need  not  be  free.  As,  however,  certain  mona- 
mines  are  not  capable  of  reacting  in  this  sense,  as,  for  example, 
ortho  substituted  monamines  such  as  mesidine  and  adjacent 
metaxylidine  do  not  form  saffranine  with  indamines  [41],  it  may 
be  conjectured  that  the  monamine  not  only  becomes  connected 
through  its  nitrogen  atom,  but  also  through  an  ortho  position  in 
the  ring,  This  assumption  receives  further  confirmation  from  the 
fact  that  the  formula  of  the  simplest  saffranine  cannot  be  sym- 
metrical, as  the  amido-groups  react  differently.  Two  different 
dialkyl  saffranines,  each  substituted  in  one  amido-group,  may  be 
prepared,  each  yielding  a  diazo-compound,  and  therefore  each 
containing  one  free  amido-group. 

Numerous  formulae  have  been  proposed  to  express  the  constitu- 
tion of  the  simplest  saffranine  in  accordance  with  the  above  facts; 
that  of  Witt,  however,  alone  fulfils  the  necessary  conditions. 
According  to  Witt  the  formation  of  saffranine  from  the  simplest 
indamine  and  aniline  proceeds  as  shown  in  the  following  schematic 
equation  : — 

NH  NH, 


HC1    H 


+4H 


Aniline 
hydroehloride. 


11 


NH, 


NH2 

Phenosaflranine  hydrochloride. 
Indamine. 

According  to  this  assumption   the  aniline  becomes  connected 
with  the  nitrogen  atom  of  the  diphenylamine  through  its  benzene 


AZINE  DYESTUFFS.  179 

ring,  and  a  derivative  of  triphenylamiiie  is  formed,  the  indamine 
link  being  dissolved.  The  nitrogen  atom  of  the  aniline  simul- 
taneously enters  one  benzene  chain  of  the  indamine,  in  the  ortho 
position  to  the  diphenylamine  nitrogen  atom,  and  the  nitrogen 
atoms  become  linked  and  form  the  azine  ring.  This  saffranine 
formula  may  be  shortly  written  thus  :  — 

/N\ 
H2N-C6H3<|>C6H4, 

N 


and  corresponds  completely  with  the  properties  of  the  compound, 
Here  the  amido-groups  have  different  values,  and  this  explains 

the  isomerism  of  the  alkyl-substitution  products.     The  pentatomic 

nitrogen  atom,  simultaneously  linked  with  chlorine  and  benzene, 

offers  distinct  reason  for  the  stability  of  the  monoacid*  saffranine 

salts. 

Further   evidence  is  afforded  by  the  fact   that  the   saffranine 

base  contains  one  molecule  of  water,  and  that  other  phenylazonium 

compounds  have  been  prepared  synthetically. 

Witt  obtained  such  a  compound  by  action  of  phenanthrene- 

quinone  on  orthoamidophenyl-/3-naphthylamine, 
H2N—  C10H6—  NH—  C6H5, 

and  ascribes  the  following  formula  to  it  :— 

N 
C10H6<  [  >C14H8. 

N 

OH    Csl15 

The  dyestuffs  obtained  by  action  of  nitrosodimethylaniline 
or  oE  quinonedichlorimide  on  phenyl-/3-naphthylamine  are  also 
probably  members  of  this  class  of  compounds  [50,  52]  . 

The  monoacid  salts  of  the  saffranine  series  are  generally  red  ;  the 
introduction  of  alcohol  radicals  into  the  amido-groups  makes  the 
shade  more  violet,  while  the  introduction  of  methoxyl  and  ethoxyl 
groups  into  the  benzene  ring  tends  to  produce  yellower  shades. 

The  saffranines  are  dyed  on  cotton  mordanted  with  tannic  acid, 
and  produce  the  shade  of  their  monoacid  salts.  Unmordanted 
cotton  is  capable  of  fixing  small  amounts  of  saffranine. 

The  diacid   salts   are   produced   by  concentrated  hydrochloric 

N2 


180  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

acid  and  are  blue ;  the  green  triacid  salts  are  obtained  with  con- 
centrated sulphuric  acid.  Both  are  only  capable  of  existence  in 
presence  of  excess  of  acid,  and  are  decomposed  by  water  with 
formation  of  a  monoacid  salt.  The  bases  may  be  obtained  by 
decomposition  of  the  sulphates  with  barium  hydrate;  they  are  of 
the  same  colour  as  the  monoacid  salts,  and  are  easily  soluble  in 
water.  They  form  carbonates  with  carbonic  acid. 

The  saffranines  yield  leuco-compounds  on  reduction,  which  are 
pretty  stable  in  acid  solution,  but  are  almost  immediately  oxidised 
to  the  original  dyestuff  in  presence  of  alkalies.  If  the  reduction 
be  effected  with  acid  stannous-chloride  solution,  one  molecule  of 
saffranine  is  found  to  require  one  molecule  of  stannous  chloride, 
showing  that  two  atoms  of  hydrogen  are  required  for  the  con- 
version of  saffranine  into  its  leuco-base. 

Phenosaffranine,  by  continued  boiling  with  zinc  powder  and 
hydrochloric  acid,  may  be  converted  into  a  very  stable  colourless 
base,  C18H19N30. 

Besides  the  reactions  already  mentioned,  saffranines  are  also 
formed  by  action  of  amines  on  amidoazo- compounds  [45],  by 
oxidation  of  the  latter,  and  by  oxidation  of  the  mauveines  [28] . 
The  formation  from  amidoazo -com  pounds  comes  under  one  of  the 
general  methods,  as  it  doubtless  depends  on  the  splitting  up  of  the 
azo-compound  into  a  paradiamine  and  a  monamine. 

The  manufacture  of  the  saffranines  is  always  effected  by  the 
process  which  depends  on  the  oxidation  of  one  molecule  of  a 
paradiamine  with  two  molecules  of  a  monamine.  The  bases 
necessary  are  obtained  by  reduction  of  amidoazo-compounds. 
Orthotoluidine  ("  Echappes/'  the  recovered  oil  from  Magenta- 
manufacture,  consisting  of  orthotoluidine  and  aniline,  may  be  used) 
is  submitted  to  the  action  of  sodium  nitrite  and  hydrochloric  acid, 
whereby  a  mixture  of  amidoazotoluene  and  orthotoluidine  is 
obtained ;  or,  if  Echappes  are  used,  a  mixture  of  amidoazotoluene, 
amidoazotoluenebenzene,  amidoazobenzene,  aniline,  and  ortho- 
toluidine is  produced.  The  mixture  is  then  reduced  with  zinc  or 
iron  and  hydrochloric  acid,  the  result  in  the  simplest  case  being  the 
production  of  a  mixture  of  one  molecule  paratoluylenediamine  and 
two  molecules  of  orthotoluidine,  while  the  principal  products  from 
the  mixture  of  bases  are  toluylenediamine  and  paraphenylenedia- 
mine  with  orthotoluidine  and  aniline.  In  any  case  the  mixture  is 
treated  in  dilute  neutral  solution  with  potassium  bichromate  and 
boiled,  or  the  oxidation  may  be  effected  by  manganese  oxide 


AZINE   DYESTUFFS.  181 

(Weldon  mud)  in  presence  of  an  organic  acid.  The  first  product  is 
an  indamine  which  yields  a  saffraiiine  on  further  oxidation  with 
the  moriamine.  Violet  dyestuffs  are  formed  along  with  the 
saflranine,  and  these,  being  less  basic,  may  be  separated  by  soda  and 
chalk,  and  the  saffranine  remaining  in  solution  is  salted  out. 
The  tolusaffranines  are  the  only  ones  of  importance,  and  their 
chief  use  is  in  cotton-dyeing.  In  conjunction  with  yellow  dye- 
stuffs  (chryso'idine,  aurarnine,  turmeric)  they  produce  shades 
similar  to  Turkey  red,  but  of  course  inferior  as  regards  fastness. 
The  saffranines  are  also  used  in  silk-dyeing  and  produce  beautiful 
rose  shades. 

Phenosaffranine  [22,  1,  2,  3]. 
C18H14N4. 

This  compound  was  first  obtained  by  Witt  by  the  oxidation  of 
one  molecule  of  paraphenylenediamine  with  two  molecules  of 
aniline  [4].  It  may  also  be  obtained  by  oxidation  of  equal 
molecules  of  aniline  and  paradiamidodiphenylaimne  [1]. 

The  free  base  may  be  obtained  by  decomposing  the  sulphate 
with  an  exactly  equivalent  quantity  of  barium  hydrate.  On 
evaporating  the  resulting  solution  in  vacua,  the  base  suddenly 
crystallises  out  in  green  leaflets,  and  is  then  found  to  have  lost  its 
easy  solubility  in  water. 

The  composition  of  the  base  dried  at  100°  corresponds  to  the 
formula 


At  150°  it  loses  about  \  molecule  of  water. 

Saffranine  base  is  not  very  stable  ;  it  loses  ammonia  on  boiling 
with  water. 

The  alcoholic  solutions  of  the  base  and  its  salts  fluoresce 
strongly,  while  this  property  is  entirely  absent  in  aqueous  solutions. 

The  hydrochloride,  C18H14N4,HC1,  crystallises  from  dilute  hydro- 
chloric acid  in  brilliant  green  leaflets,  and  from  water  in  long 
steel-blue  needles.  Its  solution  has  a  fine  red  colour.  It  is  pre- 
cipitated from  its  solutions  by  salt  and  by  strong  hydrochloric  acid. 

Nitrate,  C18H14N4HNO3,  forms  green  crystals  sparingly  soluble 
in  water,  and  almost  insoluble  in  dilute  nitric  acid  [1,  2]. 

The  sulphate,  C1SHUN4H2SO4,  forms  steel-blue  needles. 

Platinum  double  salt  [1],  (C18H14N4HC1)2  PtCl4,  forms  lustrous 
golden  leaflets,  insoluble  in  water. 


182  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Diacetyl-hydrochloride  [1],  (C18H12N4)  (C2H3O)2HC1,  is  ob- 
tained by  the  action  of  acetic  anhydride  and  sodium  acetate  on 
phenosaffranine  hydrochloride.  It  forms  lustrous  brown  leaflets, 
and  dissolves  in  alcoholic  potash  with  a  violet  colour.  It  is 
decomposed  on  boiling  with  dilute  sulphuric  acid,  acetic  acid  and 
phenosafFranine  being  produced. 

Diazo-compounds  [1]. 

The  diazochloride, 

C18H12N8HC1 


is  formed  by  action  of  nitrous  acid  on  the  (blue)  acid  solution  of 
phenosaffranine  hydrochloride.  The  solution  of  '  the  compound  is 
blue  like  the  diacid  saffranine  salts,  but  unlike  these  does  not 
change  colour  on  dilution.  Its  platinum  double  salt  forms  broad 
blue  needles. 

The  gold  salt,  C18H13N5Cl2(AuCl3)2,  forms  greenish-grey  needles. 
On  boiling  with  water  two  molecules  of  nitrogen  are  evolved.  On 
boiling  the  diazo-compound  with  alcohol  the  base  C18H13N3  is 
formed  (see  below)  . 

A  tetrazo-compound  of  safFranine  may  be  obtained  in  solution 
by  treating  the  green  solution  of  phenosaffranine  in  concentrated 
sulphuric  acid  with  nitrous  acid  [1],  The  colour  of  the  solution 
is  not  changed  on  dilution.  On  boiling  with  alcohol  a  violet  base, 
forming  yellow  salts,  is  produced.  The  chloride  of  this  compound 
is  probably  phenazinephenyl-chloride, 


H4, 


Ci 


the  mother  substance  of  the  saiFranines  [43].  It  is  interesting  to 
note  that  the  colour-reactions  of  this  compound  with  acids  are 
exactly  the  same  as  those  of  the  acetylated  s  aff  rani  nes,  from  which 
it  appears  that  the  acetylation  has  the  same  effect  as  the  removal 
of  the  amido-groups  [43].  The  compound  in  question  is  more 
easily  obtained  from  the  base  C18H13N3,  the  intermediate  product 
in  this  case  being  a  yellow  diazo-compound. 


AZINE  DYESTUFFS.  183 

a-Dimethylphenosaffran  ine  [2  ]  , 

C18H12N4(CH3)2, 

is  formed  by  oxidation  of  one  molecule  of  dimethylparaphenylene- 
diamine  with  two  molecules  of  aniline. 

The  hydro  chloride,  C20H18N4_,HC1,  is  a  magenta-red  dyestuff 
known  commercially  as  Fuchsia. 

The  nitrate,  C20H18N4,HNO3,  forms  lustrous  green  needles. 

Platinum  double  salt,  (C20H18N4HCl)2PtCl4. 

(3-DimetJ^lphenosqff'ranine  [41,  43]. 

This  compound,  isomeric  with  the  above,  is  obtained  by  oxida- 
tion of  one  molecule  of  paraphenylenediamine  with  one  molecule 
of  dimethylaniline  and  one  molecule  of  aniline.  Its  nitrate  forms 
brown  leaflets.  For  the  crystallographic  comparison  of  the 
nitrates  see  [43]. 

Tetramethylphenosaffranine  [2  ]  . 


This  dyestuff  is  formed  by  oxidation  of  one  molecule  of  di- 
methylparaphenylenediamine,  one  molecule  of  dimethylaniiiue, 
with  one  molecule  of  aniline. 

Hydrochloride,  C22H22N4,HC1. 

Nitrate,  C22H22N4,HNO3,  is  a  fluorescent  dyestuff  forming 
brownish-violet  thick  crystals. 

Diethylsaffranines  [1]. 

C18H12N4(C2H5)2. 

a.  From  one  molecule  of  dietbylparaphenylenediamine  and  two 
molecules  of  aniline,  and 

/3.  From  equal  molecules  of  paraphenylenediamine,  diethyl- 
aniline,  and  aniline. 

The  hydrochlorides  of  both  modifications  form  brilliant  green 
needles,  which  are  violet-red  dyestufPs. 

The  /3-hydrochloride  is  much  more  soluble  in  water  than  the 
a-compound. 

Platinum  salt,  (C22H23N4Cl)2PtCl4, 


184  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Acetyl  derivatives  [1]. — Both  diethylsaffranines  yield  basic 
monoacetyl  derivatives  on  heating  with  acetic  anhydride  and 
sodium  acetate.  The  hydrochlorides  possess  the  formula 

a2H23N4Cl,C3H30, 

and  form  lustrous  brown  needles,  soluble  in  water  and   alcohol 
with  a  violet  colour.     The  alcoholic  solutions  do  not  fluoresce. 


DiazO'Compoimds. 

When  treated  with  nitrous  acid  the  diethylsaffranines  yield 
diazo-compounds,  analogous  to  the  primary  diazo-compounds  of 
pheiiosaffranine.  The  solutions  have  a  greenish-blue  colour. 

The  chloride  corresponds  to  the  formula 

C22H20N3HC1-N=NC1. 

Platinum  salt,  C22H21N5Cl2PtC]4,  forms  almost  black  needles 
with  a  coppery  lustre. 

The  fact  that  both  modifications  of  dimethyl-  and  diethyl- 
saffranine  yield  diazo-compounds,  gives  a  certain  proof  of  the 
presence  of  two  amido-groups  in  saffraniue. 

Two  isomeric  monoethylsaffranines  may  be  obtained  in  an 
analogous  manner. 

The  constitution  of  the  a-  and  /3-compounds  is  probably  ex- 
pressed by  the  formulae 

(CH3)2N-C6H3V;C6H4. 

Cl7   XC6H4NH2 

a-Dimethylsafframne. 

/Nx 
H,N-C,H/  |  Wi 

XN7 

Cl   XC6H4N(CH3)2 
j3-Dimetliylsafframne. 

(Compare  Indamines.) 


AZINE   DYESTUFFS.  185 

Tetraethylphenosaffranin e  [1  ] , 

C18H10N4(C2H5)4, 

is  obtained  by  oxidation  of  equal  molecules  of  diethylparapheny- 
lenediamine,  diethylaniline,  and  aniline.  It  forms  a  zinc  chloride 
double  salt  which  forms  beautiful  crystals  with  a  golden-yellow 
lustre.  It  is  a  bluish-violet  dyestuff  and  exhibits  a  magnificent 
fluorescence  on  silk,  but  is  speedily  altered  on  exposure  to  light. 
It  is  known  in  commerce  as  Amethyst-Violet. 

Platinum  double  salt,  (C26H30N4,HCl)2PtCl4. 

Tetraethylsaffranine  does  not  react  with  either  nitrous  acid  or 
acetic  anhydride. 

Two  dyestuifs,  the  constitution  of  which  has  not  been  definitely 
ascertained,  but  which  from  their  method  of  preparation  belong 
to  the  saffrauine  series,  are  Eubramine  and  Girofle. 

Rubramine  is  prepared  by  acting  on  orthotoluidine  with  nitroso- 
dimethylaniline  in  hydrochloric  acid  solution.  It  comes  into 
commerce  as  greenish-brown  powder,  and  produces  a  fine  red- 
violet  shade  on  cotton  mordanted  with  tannic  acid. 

Girofle,  probably  a  homologue  of  a-dimethylsaffranine  (Fuch- 
sia), is  obtained  by  acting  onxylidine  with  nitrosodimethylaniline. 
It  is  used  for  shading  alizarine  violet  and  reds. 

Tolusaffranine  [24]. 

C21H20N4. 

Hydrochloride,  C21H20N4)HC1,  forms  fine  reddish-brown  needles 
soluble  in  water  and  alcohol. 

Platinum  double  salt,  (C21H20N4HCl)2PtCl4,  forms  a  yellowish- 
red  crystalline  powder. 

The  nitrate,.  C21H20N4,HNO3,  forms  reddish-brown  needles 
sparingly  soluble  in  cold  water. 

Pier  ate,  C21H20N4C6H2(NO2)3,  OH,  forms  reddish-brown  needles 
insoluble  in  water  and  alcohol. 

Besides  the  ortho-compound,  formed  by  oxidation  of  one  mole- 
cule of  paratoluylenediamine,  there  exists  a  second  one  which  is 
formed  from  equal  molecules  of  toluylenediamine,  aniline,  and 
orthotoluidine,  and  is  distinguished  from  the  former  by  its  lesser 
solubility.  Both  come  into  commerce  as  hydrochlorides.  The 


186  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

latter,  if  prepared  as  usual  from  a  mixture  of  aniline  and  tolui- 
dine,  generally  contains  a  lower  homologue,  C20H18N4.  These 
dyestuffs  differ  but  little  in  shade,  and  produce  on  silk,  wool,  and 
cotton  prepared  with  tannic  acid,  tones  about  halfway  between 
magenta  and  ponceau.  Dyestuffs  which  are  to  be  regarded 
as  oxymethyl-  and  oxyethyl-derivatives  of  phenosaffraiiine  are 
produced  by  oxidation  of  paraphenylenediamine  with  two  mole- 
cules of  orthoanisidine  or  two  molecules  of  orthoamidophenetol. 
The  orthoanisidine  compound  has  probably  the  composition : — 

C18H12(OCH3)2N4. 

Similar  bodies  are  formed  if  the  orthoanisidine  is  partly  replaced 
by  paranisidine  or  another  primary  monamine.  These  dyestuffs 
are  especially  characterized  by  their  pure  yellow  shade.  When 
dyed  on  silk  they  fluoresce  strongly,  the  shades  obtained  resem- 
bling those  produced  by  some  of  the  cosines.  Owing  to  their 
high  price,  however,  they  have  not  been  used  on  a  large  scale. 


The  compound  C18H13N3  [43,  49]  has  already  been  mentioned 
as  the  product  obtained  on  boiling  the  primary  diazo-compound 
of  phenosaffranine  with  alcohol.  Its  salts  have  a  magenta-red 
colour  and  do  not  fluoresce  in  alcoholic  solution.  Concentrated 
sulphuric  acid  dissolves  them  with  a  yellowish-green  colour,  and 
on  dilution  the  colour  changes  through  green  to  red ;  the  blue 
phase  does  not  occur. 

Nitrate,  C18H13N3,HNO3,  forms  brown,  difficultly  soluble 
needles. 

Zinc  chloride  double  salt  forms  lustrous  brown  needles. 

Acetyl  derivative,  C18H12N3C3H3O,  is  a  violet  compound  forming 
yellow  monoacid  salts. 

The  compounds  obtained  by  Witt  [52],  and  by  Nietzki  and 
Otto  [50,  51],  by  action  of  nitrosodimethylaniline  and  of  quinone- 
dichlorimide  on  phenyl-/3-naphthylamine  in  all  probability  belong 
to  this  series. 

By  action  of  quinonedichlorimide  on  phenyl-/3-naphthylamine,  a 
violet  base  is  produced  forming  magenta-red  salts. 

The  compound  dissolves  in  concentrated  sulphuric  acid  with  a 
violet  colour  which  on  dilution  changes  through  dirty  green  into 
red.  The  composition  of  the  salts  may  be  expressed  by  the 
general  formula  C22H15N3 .  R. 


AZINE  DYESTUFFS.  187 

Nitrate,  C0oH15N3;HNO3,  forms  fine  needles  or  thicker  lustrous 
green  crystals. 

The  constitution  of  the  compound  is  probably  expressed  by  the 
formula  [50]  : — 


-NIL 


The  product  of  the  interaction  of  nitrosodimethylaniline  and 
phenyl-/3-naphthylamine  is  a  bluish-violet  dyestuff,  probably  a 
dimethyl  derivative  of  the  former  [5.2]  :  Neutral  Blue. 

Nitrosodimethylaniline  reacts  with  paratoluyl-/3-naphthylamine 
also,  and  produces  a  bluish-violet  dyestuff  of  the  composition 

C25H22N3C1. 

From  the  salts,  a  red  base  may  be  separated,  which  dissolves  in 
alcohol  with  an  orange-yellow  fluorescence. 

The  compound  dissolves  in  concentrated  sulphuric  acid  with  a 
red-violet  colour,  which  on  dilution  changes  through  green  and 
blue  to  violet.  The  nitrate  is  very  sparingly  soluble  [52] . 

Saffranol. 
C18H12N3(OH)2. 

This  compound  is  formed  by  continued  boiling  of  phenosaffra- 
nine  with  baryta  water,  or  alcoholic  potash  solution.  It  may  be 
regarded  as  phenosaffraniue  in  which  both  amido-groups  are 
replaced  by  hydroxyl.  The  compound  agrees  with  this  assumption 
inasmuch  as  it  possesses  simultaneously  acid  and  weak  basic 
properties. 

Saffranol  forms  brass-coloured  leaflets,  almost  insoluble  in 
indifferent  solvents,  but  easily  in  ammonia  and  alkalies  with  a 


188  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

deep  carmine-red  colour.  It  is  separated  from  these  solutions  by 
acids,  and  produces  the  sparingly  soluble  salts  if  an  excess  be 
present. 

It    forms    a    red    diacetyl-compound,    which    yields     yellow, 
sparingly  soluble  salts  with  acids  [49]. 


Indazine  M  [53], 

Cl^  C6H 

X 

(CH3)2-N-C6H3(^\ 
C34H30N6C12  =  -  - 

(CH3)2-N-C6H3(  |  / 
N 


is  produced  by  action  of  nitrosodimethylaniline  hydrochloride 
on  diphenylmetaphenylenediamine.  It  dyes  fine  blue  shades  on 
cotton  prepared  with  tannic  acid. 


Sasle  Blue  [54]. 

/N 
C32H29N4C1=(CH3)2NC6H3;  |  ;C10H5N-C6H4CH3 

XN/ 

Clc'6H4CH3 

This  dyestuif  is  obtained  by  the  action  of  nitrosodimethylaniline 
chlorhydrate  on  the  ditolylnaphthylenediamine  obtained  by  heating 
a-dioxynaphthalene  (M.P.  180°)  with  paratoluidine  and  parato- 
luidine  hydrochloride.  The  dyestuff  forms  a  brownish  crystalline 
powder,  soluble  in  water  with  a  bluish-violet  colour.  It  dissolves 
in  concentrated  sulphuric  acid  with  a  greenish-blue  colour,  which 
on  dilution  changes  through  green  to  violet,  a  bluish-violet 
precipitate  being  formed.  Basle  blue  is  a  basic  dyestuff  and  is 
best  dyed  on  cotton  prepared  with  tannic  acid  and  tartar  emetic. 


AZINE  DYESTUFFS.  189 

Azine  Green  [55] 

is  analogous  to  the  above  in  constitution,  and  results  from  the 
action  of  nitrosodimethylaniline  hydrochloride  on  the  diphenyl- 
naphthylenediamine  obtained  from  dioxynaphthylene,  M.P.  216°. 
It  is  a  basic  dyestuff,  producing  dark  green  shades  which  are 
pretty  fast. 

5.  MAGDALA  RED. 

This  dyestuff  has  been  long  known,  and  was  investigated  almost 
twenty  years  ago  by  Hofmann  [27]  ;  but  from  the  recent  researches 
of  Julius  [44]  it  appears  that  the  earlier  formula,  C30H21N3,  is 
incorrect,  and  that  its  composition  is  analogous  to  that  of  the 
saffranines,  its  formula  being  C30H20N4.  Accordingly  Magdala 
red  may  be  regarded  as  a  saffranine  of  the  naphthalene  series. 
Indeed  the  great  stability  of  the  dyestuff,  its  properties,  and  the 
strong  fluorescence  of  its  salts  are  strong  arguments  in  favour  of 
this  assumption. 

Magdala  red  is  obtained  by  heating  a-amidoazonaphthalene  with 
a-naphthylamine  hydrochloride  in  glacial  acetic  acid  solution. 
The  yield  is  extremely  small.  A  better  yield  is  claimed  in  a  more 
recent  modification  of  the  above  process,  in  which  a  mixture  of 
the  hydrochlorides  of  a-naphthylamine  and  paranaphthylenedia- 
mine  is  heated  with  amidoazonaphthalene  to  130-140°  till  the 
melt  has  a  pure  red  colour. 

Analogous  dyestuffs  may  also  be  obtained  from  mixtures  of 
naphthylenediamine  hydrochloride  and  amidoazobenzene,  or  with 
naphthylenediamiiieaniline  and  amidoazobenze  [56]  . 

Magdala  red  hydrochloride  forms  lustrous  green  needles, 
sparingly  soluble  in  water,  more  easily  in  alcohol.  The  salt  is  not 
decomposed  by  ammonia  or  caustic  soda  [27].  The  sulphate 
forms  large  green  needles  [45].  The  picrate  and  platinum  double 
salt  are  sparingly  soluble  in  alcohol. 

The  alcoholic  solutions  of  the  salts  exhibit  a  magnificent  yellow 
fluorescence,  which  surpasses  that  of  any  of  the  saffranines.  The 
salts  dissolve  in  concentrated  sulphuric  acid  with  a  bluish-black 
colour. 

Magdala  red  still  finds  a  slight  application  in  special  cases  in 
silk-dyeing,  but  owing  to  its  enormous  price  has  been  almost 
entirely  superseded  by  rhodamine. 


190  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

6.  MAUVEINE  [28]. 
C27H24N4. 

Mauveine  was  the  first  aniline  dyestuff  prepared  on  a  large  scale 
(Perkin,  1856) ,  and  is  certainly  closely  related  to  the  saffranine 
dyestuffs.  Like  these,,  it  has  strong  basic  properties,  and  gives 
similar  reactions  with  sulphuric  acid.  Finally,  a  saffranine  (para- 
saffranine,  C20H18N4  [28])  is  formed  by  oxidation  of  mauveine  in 
acetic  acid  solution.  The  fluorescence  characteristic  of  alcoholic 
saffranine  solution  is,  however,  absent  with  mauveine. 

Free  mauveine  forms  a  black  crystalline  powder,  insoluble  in 
water,  soluble  in  alcohol  with  bluish-violet  colour.  It  is  a  strong 
base,  taking  up  carbonic  acid  from  the  air,  and  capable  of  ex- 
pelling ammonia  from  its  salts. 

It  forms  three  series  of  salts  with  acids,  and  these  are  exactly 
analogous  to  those  of  the  saffranines.  The  triacid  salts  are  green, 
and  only  obtainable  with  concentrated  sulphuric  acid.  The 
diacids  are  blue,  and,  like  the  former,  are  decomposed  by  water. 
The  monoacid  salts  are  crystalline,  have  a  reddish-violet  colour, 
and  are  stable. 

The  mauveine  salts  do  not  produce  their  characteristic  reddish- 
violet  colour  when  dyed  on  wool,  but  the  shade  is  the  bluer  one 
of  the  free  base. 

Hydro  chloride,  C27H24N4,HC1,  forms  small  lustrous  green 
prisms,  sparingly  soluble  in  water,  easily  in  alcohol. 

Acetate,  C27H24N4,C2H4O2,  forms  lustrous  green  prisms. 

Carbonate,  green  prisms  with  a  metallic  lustre.  Is  decomposed 
on  boiling  or  drying. 

Platinum  double  salt,  (C27H24N4,HCl)2PtCl4,  forms  large  golden 
crystals,  sparingly  soluble  in  alcohol. 

C27H24N4(HCl)2PtCl4,  dark  blue  precipitate. 

C27H24N4,AuCl3,  crystalline  powder. 

Ethyl  derivative,  C27H23(C2H5)N4,  is  formed  by  action  of  ethyl- 
iodide  on  mauveine  in  alcoholic  solution. 

Hydrochloride,  C29H28N4,HC1,  forms  a  reddish-brown  crystalline 
powder,  sparingly  soluble  in  water,  easily  in  alcohol,  forming  a 
purple  solution. 

(CsoHagN^HClJaPtCLt,  golden-green  precipitate. 

Iodide,  C29H28N4,HI,I2,  golden-green  crystals. 


AZINE  DYESTUFFS.  191 

Pseudomauveine,  C24H20N4,  is  obtained  by  oxidation  of  pure 
aniline,  and  is  very  similar  to  mauveine. 

A  dyestuff  probably  identical  with  pseudomauveine  has  been 
obtained  synthetically  by  Fischer  and  Hepp,  by  action  of  para- 
nitrosodiphenylamine  on  aniline  hydrochloride  [51]. 

Hydrochloride,  C24H20N4,HC1,  green  crystals. 

Platinum  double  salt,  (C24H20N4,HCl)2PtCl4. 

The  mauveine  dyestuffs  are  formed,,  although  only  in  small 
quantities,  by  oxidation  of  primary  monamines  in  neutral  solution 
with  potassium  bichromate,  cupric  chloride,  lead  peroxide,  and 
other  oxidising  agents.  It  has  not  been  determined  with  certainty 
what  monamines  are  capable  of  yielding  dyestuffs  of  this  class ;  but 
it  is  probable  that  the  mauveine  C27H24N4  is  formed  from  three 
molecules  of  toluidine  (ortho  and  para?)  and  one  molecule  of 
aniline,  according  to  the  equation  : — 

3C7H9N  +  C6H7N  =  C27H24N4  +  10H. 

It  is  not  certain  if  the  violet  coloration  obtained  with  bleaching- 
powder  and  aniline  solution  is  due  to  the  formation  of  mauveine, 
although  this  is  generally  stated. 

Mauveine  is  now  of  little  but  historical  interest.  It  was 
obtained  first  by  Perkin  by  oxidation  of  (impure  ?)  allyltoluidine 
with  potassium  bichromate.  It  is  still  manufactured  in  small 
quantities,  and  used  in  printing  English  postage-stamps  and  for 
tinting  silk  for  production  of  white.  At  present  mauveine  salts 
are  met  with  in  commerce  under  the  designation  Rosolane. 

A  synthetical  process  for  production  of  a  series  of  saffranine 
dyestuffs  closely  related  to  mauveine  is  the  subject  of  a  recent 
patent.  It  consists  in  the  oxidation  of  one  molecule  of  para- 
midodiphenylamine,  or  one  of  its  homologues,  with  two  molecules 
of  aniline,  orthotoluidine,  or  xylidine  [58] . 

The  dyestuffs  have  a  violet  colour,  and  in  general  closely 
resemble  the  mauveines. 

Mauveine  may  be  regarded  as  a  phenylated  saffranine, 
C21H19N4(C6H5).  Certainly  the  violet  dyestuffs  obtained  by 
action  of  aniline  on  saffranine  are  totally  different  from  mauveine, 
and  apparently  belong  to  the  Induline  series.  The  fact  that 
mauveine  cannot  be  obtained  in  this  manner  is,  however,  no 
argument  against  the  assumption  that  it  is  a  phenylsaffranine,  as 
all  these  dyestuffs  undergo  a  complete  change  in  constitution  on 
boiling  with  aniline. 


192  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


CHAPTER  VIII. 

ANILINE   BLACK. 

MOST  oxidising  agents  acting  in  acid  solution  produce  a  peculiar 
dyestuff  with  aniline  salts.  This  body  is  characterised  by  its 
dark  colour,  and  its  sparingly  solubility  in  most  solvents.  Its 
formation  has  been  observed  by  the  action  of  the  following 
agents  : — Manganese  dioxide  [1]  ;  lead  peroxide,  chromic  acid  [2]; 
ferric  salts  [3]  ;  ferricyanides  [3]  ;  permanganates  [5]  ;  chloric  acid 
alone  [6],  or  chlorates  in  presence  of  certain  metallic  salts  [7], 
amongst  which  vanadium,  cerium,  and  copper  compounds  are 
the  most  effective.  In  all  cases  these  oxidising  agents  withdraw 
hydrogen  from  the  aniline  molecule. 

The  formation  of  aniline  black  from  chlorates  and  the  above- 
mentioned  metallic  salts  is  especially  of  interest,  inasmuch  as 
very  small  quantities  of  the  latter  suffice  for  the  oxidation  of 
relatively  large  quantities  of  aniline.  Vanadium  has  the  most 
powerful  action  in  this  respect.  According  to  Witz  [8],  one  part 
of  vanadium,  aided  by  the  necessary  amount  of  a  chlorate,  is 
sufficient  to  convert  270,000  parts  of  an  aniline  salt  into  aniline 
black.  After  vanadium,  cerium  and  copper  are  the  most  effective, 
iron  having  considerably  less  action. 

It  is  evident  from  this  that  the  metallic  compounds  act  only 
as  oxygen-carriers.  From  the  fact  that  only  those  metals  which 
form  several  oxygen  or  chlorine  compounds  are  capable  of  pro- 
ducing the  desired  action,  it  is  probable  that  the  higher  metallic 
oxides  effect  the  ^xidation  of  the  aniline,  and  that  these  oxides 
are  continuously  regenerated  by  the  chlorate  present.' 

If  cupric  chloride  is  applied  with  an  insufficient  quantity  of 
chlorate,  it  is  possible  to  detect  the  formation  of  cuprous  chloride 


ANILINE  BLACK.  193 

in  the  mixture.  For  the  production  of  aniline  black  from  solu- 
tions it  is  necessary  that  the  latter  be  acid.  The  formation  of 
black  from  chlorate  and  copper  salts  may,  however,,  take  place  in 
presence  of  excess  of  aniline,,  if  the  mixture  be  allowed  to  dry,  as 
is  the  case  in  black-printing. 

The  formation  of  aniline  black  from  chloric  acid  and  aniline 
likewise  only  takes  place  on  drying.  Chlorate  of  aniline  is  pretty 
stable  in  solution,  but  if  the  crystallised  salt  be  dried,  it  is  con- 
verted into  aniline  black,  which  generally  retains  the  crystalline 
form  of  the  chlorate  [33].  Finally,  aniline  black  is  formed  at 
the  positive  pole  on  the  electrolysis  of  salts  of  aniline  [10,  16]. 

The  substance  formed  in  all  these  reactions  exhibits  practically 
the  same  properties.  It  consists  principally  of  a  compound  of 
weak  but  distinctly  basic  character.  The  base  in  the  free  state 
has  a  dark  violet,  almost  black,  colour,  while  its  salts  are  dark 
green.  The  latter  are  unstable  and  partly  decomposed  by  water. 
It  is,  however,  difficult  to  remove  the  whole  of  the  acid  by  washing. 

The  base  is  almost  insoluble  in  most  solvents.  It  dissolves 
with  difficulty  in  aniline  with  a  violet  colour,  which  on  long 
standing  changes  to  brown  [11]. 

It  dissolves  somewhat  more  easily  in  phenol,  with  a  bluish-green 
colour.  With  concentrated  sulphuric  acid  it  forms  a  violet 
solution,  from  which  water  precipitates  the  dark  green  sulphate. 
With  fuming  sulphuric  acid  it  yields  sulphonic  acids  differing 
according  to  the  temperature  and  duration  of  the  reaction.  The 
sulphonic  acids  are  green  in  the  free  state,  and  form  easily 
soluble  salts-  with  the  alkalies.  These  latter  have  a  violet-black 
colour. 

The  instability  of  the  salts  of  aniline  black  renders  it  difficult 
to  obtain  them  with  a  constant  amount  of  acid.  The  hydro- 
chloride  loses  hydrochloric  acid  on  drying,  and  does  not  form  a 
definite  compound  with  platinum  chloride. 

With  acetic  anhydride,  aniline  black  yields  an  acetyl  derivative, 
which  possesses  little  colour,  and  which  is  insoluble  in  concen- 
trated sulphuric  acid  [34]. 

Methyl  and  ethyl  iodides  appear  to  produce  substitution- 
derivatives,  but  differ  only  slightly  from  the  original  compound 
[34].  On  treating  with  potassium  bichromate,  aniline  black 
gives  a  violet-black  compound,  which  contains  chromic  acid  and 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

appears  to  be  the  chromate  of  the  black  base    (Chrome-black) 
[34].     It  is  not  turned  green  by  acids. 

Energetic  oxidising  agents,  for  example  chromic  acid  in  a 
strongly  acid  solution,  convert  aniline  black  into  quinoue  [34], 
Reducing  agents  form  an  insoluble  leuco-compound,  which 
oxidises  slowly  in  presence  of  acids,  and  rapidly  in  presence  of 
alkalies,  aniline  black  being  reproduced. 

If  the  reduction  be  more  energetic, — for  example,  with  tin  and 
hydrochloric  acid,  or  hydriodic  acid  and  phosphorus, — the  black 
is  completely  split  up,  paraphenylenediamine,  paracliamidodiphe- 
nylamine  [34],  and  small  quantities  of  diphenylamine  being 
formed.  If  the  black  is  submitted  to  dry  distillation,  aniline, 
paraphenylenediamine,  diamidodiphenylamine,  and  diphenylpara- 
phenylenediamine  are  produced  [33] . 

By  continued  action  of  aniline  on  aniline  black,  products 
resembling  the  indulines  are  formed.  One  of  these  has  been 
isolated,  and  is  a  blue  dyestuff  of  the  formula,  C36H29N5  or  C36H31N5 
[18]. 

This  substance  resembles  the  indulines, .  the  base  having  a  red 
colour  in  alcoholic  or  ethereal  solution,  while  the  salts  are  blue. 
It  probably  bears  the  same  relationship  to  aniline  black  as  the 
higher  indulines  discovered  by  Witt  and  Thomas  do  to  the  indu- 
line  C18H16N3.  (See  page  202.) 

The  numerous  analyses  made  of  aniline  black  show  that  it  is 
formed  from  aniline  by  simple  abstraction  of  hydrogen.  The 
values  obtained  approximate  nearly  to  the  simple  expression, 
C6H5N.  Naturally  the  molecule  corresponds  to  a  multiple  of 
this  formula,  but  the  instability  of  the  salts  has  hitherto  rendered 
it  impossible  to  determine  the  molecular  formula  accurately. 

The  following  formulae  have  been  proposed  by  investigators  in 
this  direction  : — 

1."  C12H10N2. 
2.''C18H15N3. 

3.  C24H20N4. 

4.  C30H25N5. 

No.  1  was  proposed  by  Kayser  [12],  No.  3  by  Goppelsroeder 
[15],  and  Nos.  2  and  4  are  due  to  Nietzki. 

Formula  No.  4  was  based,  principally  on  the  formation  of  the 
above-named  blue  dyestuff,  which  was  regarded  as  phenylated 


ANILINE  BLACK.  195 

aniline  black,  C30H25N5 — C6H5.  Since  then,  however,  Witt  [27] 
has  shown  that  from  the  induline  C18H15N3  dyestuffs  may  be  pro- 
duced by  the  action  of  aniline,  which  contain  five  nitrogen  atoms 
in  the  molecule,  so  that  this  argument  for  the  formula  C30H25N5 
becomes  useless. 

Determinations  of  the  amount  of  hydrogen  required  to  convert 
aniline  black  into  its  ieuco-compounds  point  nearly  to  two  atoms 
of  hydrogen  for  the  formula  C18H15N3.  This  appears  to  be  the 
correct  molecular  formula  [9] .  The  fact  that  the  analysis  of  the 
black  gives  throughout  slightly  lower  values  for  the  hydrogen, 
renders  it  possible  that  the  formula  C18H13N3  may  be  accurate. 

Some  conclusions  as  to  the  constitution  of  aniline  black  are 
obtained  from  its  decomposition  on  oxidation  and  reduction.  The 
production  of  quinone  in  the  former,  and  of  paraphenylamine,  &c., 
in  the  latter,  render  it  apparent  that  the  nitrogen  atom  of  one 
benzene  residue  enters  the  chain  of  another  benzene  residue  in  the 
para  position  to  the  nitrogen  atom.  Goppelsroeder's  formula  [15] , 
in  which  the  benzene  chains  are  represented  as  linked  in  a  circle 
of  imido-groups,  corresponds  to  this  view  to  a  certain  extent.  This 
entirely  symmetrical  formula,  however,  does  not  account  for  the 
tinctorial  character  of  the  compound  in  a  satisfactory  manner ; 
and  from  the  formation  of  a  stable  leuco- compound  it  may  be 
deduced  that  in  all  probability  at  least  two  nitrogen  atoms  of  the 
molecule  are  linked  together. 

Liechti  and  Suida  [33]  regard  the  black  from  aniline  chlorate 
as  a  chlorinated  product.  This  is  improbable,  as  on  treating 
with  concentrated  sulphuric  acid,  hydrochloric  acid  is  evolved,  and 
a  sulphate  almost  free  from  chlorine  is  produced. 

The  adoption  of  similar  processes  with  orthotoluidine  results  in 
the  formation  of  a  compound  probably  homologous  with  aniline 
black,  of  the  formula  C7H7N  [34]. 

This  compound  resembles  aniline  black  in  all  its  properties. 
The  salts  are  dark  green  and  the  free  base  is  bluish  black.  The 
latter  differs  from  aniline-black  base  by  the  fact  that  it  dissolves 
in  chloroform  with  a  bluish-violet  colour  [34] . 

Paratoluidine  does  not  form  an  analogous  compound  on  oxidation. 

Besides  the  compound  described  in  detail,  aniline  black  gener- 
ally contains  others.  One  of  these  is  the  product  of  a  less 
energetic  oxidation,  and  is  distinguished  from  the  former  com- 
pound by  the  brighter  green  colour  of  its  salts  and  a  brighter  violet 

o  2 


196  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

colour  of  the  free  base.  It  also  possesses  a  considerably  higher 
degree  of  solubility  in  alcohol,  acetic  acid,  &c.  It  dissolves  in 
concentrated  sulphuric  acid  with  a  red-violet  colour.  This  sub- 
stance is  probably  the  principal  constituent  of  the  dyestuff 
formerly  sold  as  Emeraldine,  and  is  probably  identical  with  the 
product  formed  by  oxidation  of  paraphenylenediamine  with 
diphenylamine  [17]. 

An  interesting  reaction  in  which  emeraldine  is  formed  was 
observed  by  Caro  [16].  If  aqueous  solution  of  free  aniline  is 
oxidised  with  potassium  permanganate,  and  filtered  from  the 
separated  manganese  dioxide,  the  nitrate  is  a  yellowish  liquid, 
from  which  ether  takes  up  a  yellow  amorphous  compound.  This 
latter  is  converted  into  a  green  salt  of  emeraldine  by  mere  contact 
with  acids.  A  substance  possessing  the  properties  of  emeraldine 
is  formed  simultaneously  with  quinone  by  oxidation  of  paramido- 
diphenylamine.  A  larger  yield  is  obtained  if  this  base  is  oxidised 
with  an  equivalent  of  aniline,  and  in  this  case  quinone  is  not 
formed  [17].  On  further  oxidation  emeraldine  yields  a  darker 
coloured  compound,  but  it  is  doubtful  if  this  is  aniline  black.  The 
formation  of  emeraldine  from  paraphenylenediamine  and  di- 
phenylamine leads  to  the  supposition  that  it  is  a  phenylated 
iiidamine  of  the  formula  : 


C6H5N—  C6H4/ 

On  further  oxidation,  especially  with  chlorinating  agents,  ani- 
line black  yields  a  darker  product  which  is  no  longer  turned 
green  with  acids. 

On  boiling  the  acetate  or  the  hydrochloride  of  aniline  black 
with  aniline,  a  mixture  of  dyestuffs  is  formed,  one  of  which,  a  base 
of  the  composition  C36H29N5,  has  already  been  mentioned.  The  free 
base  dissolves  in  ether  with  magenta-red  colour;  its  salts  with 
acids  are  insoluble  in  water,  soluble  in  alcohol  with  a  blue 
colour  [18]. 

C36H29N5,HC1  crystallises  from  alcohol  in  small  needles  which 
have  a  coppery  lustre. 

(C36H29N5,HCl)2PtCl4  forms  a  violet  precipitate  sparingly 
soluble  in  alcohol. 

C36H29N5,HI  is  similar  to  the  hydrochloride. 

C36H29N5,C6H2(N02)3OH,  sparingly  soluble  precipitate. 


ANILINE   BLACK.  197 


TECHNICAL  ANILINE  BLACK. 

Aniline  black  in  substance  is  scarcely  ever  prepared  in  the 
colour  manufactory,  but  is  always  produced  directly  on  the  fibre. 
It  has  an  extended  application  in  calico-printing  and  cotton- 
dyeing-,  but  as  yet  is  of  little  service  in  wool-dyeing.  For  aniline- 
black  printing  innumerable  recipes  have  been  published  and 
patents  taken,  all  depending  on  one  or  other  of  the  methods  of 
formation  mentioned  in  the  introduction  to  this  chapter. 

The  oxidising  agent  most  generally  employed  is  potassium  (or 
sodium)  chlorate  in  presence  of  copper  salts  [7].  As  soluble 
copper  compounds  are  liable  to  attack  the  iron  portions  of  the 
printing-machine,  copper  sulphide  [19]  is  used.  On  printing, 
this  is  partly  converted  into  copper  sulphate,  which  then  enters 
into  the  reaction. 

For  example,  a  mixture  of  aniline  hydrochloride,  potassium 
chlorate,  and  copper  sulphide,  thickened  with  starch,  is  printed. 
The  printed  goods  are  then  aged  in  a  moist  room,  at  a  temperature 
of  about  30°,  and  the  oxidation  of  the  sulphide  to  sulphate  and  of 
the  aniline  to  black  takes  place. 

Vanadium  compounds  (vanadic  acid  and  vanadium  chloride) 
have  been  proposed  as  substitutes  for  copper  sulphide,  but  without 
much  practical  success.  Potassium  ferrocyanide  and  ferricyanide 
are  also  used  to  a  certain  extent.  A  mixture  of  these  salts  with 
aniline  salt  and  potassium  chlorate  is  printed,  and  the  goods  aged. 
The  probable  action  is  that  the  ferricyanide  oxidises  the  aniline, 
and  is  continually  regenerated  from  the  ferrocyanide  formed  by  the 
chloric  acid  present.  Thus  these  salts  play  the  part  of  oxygen 
carriers  in  a  similar  manner  to  the  copper  and  vanadium  com- 
pounds. In  the  opinion  of  technologists,  the  black  produced  by 
this  process  differs  somewhat  in  its  properties  from  that  obtained 
with  copper,  but  this  may  be  ascribed  to  the  presence  of  prussian 
blue  in  the  former.  In  place  of  the  aniline  hydrochloride  and 
potassium  chlorate,  a  mixture  of  aniline  sulphate  and  barium 
chlorate  has  recently  been  employed  in  black-printing. 

In  printing  it  is  absolutely  necessary  that  the  formation  of 
black  should  not  take  place  in  the  liquid  mixture,  as  in  this  case  it 
would  soon  become  useless.  Oxidants,  like  chromic  acid,  manga- 


198  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

nese  dioxide,  &c.,  which  act  directly  on  the  aniline,  cannot  be 
employed  in  printing. 

In  cotton-dyeing,  however,  the  case  is  just  the  opposite,  as  the 
black  formation  should  be  as  rapid  as  possible. 

For  this  purpose  the  formation  of  black  is  often  effected  by  the 
action  between  manganese  dioxide  and  aniline  salts. 

The  goods  are  treated  with  manganese  chloride,  and  then  passed 
through  an  alkaline  bath  whereby  manganous  oxide  is  precipitated 
on  the  fibre.  A  subsequent  oxidation  by  air  or  by  a  bath  of 
chloride  of  lime  serves  to  convert  this  into  peroxide,  a  bottom  of 
the  so-called  manganese-bronze  being  obtained.  On  passing  into 
an  acid  solution  of  aniline,  aniline  black  is  precipitated  on  the 
fibre  in  a  firmly  adherent  condition. 

However,  chromic  acid  is  the  oxidant  generally  employed.  An 
aniline  solution  containing  free  sulphuric  acid  is  mixed  with  a 
soluble  bichromate,,  and  the  goods  entered.  On  heating,  the  black 
is  precipitated  on  the  fibre.  In  all  cases  the  aniline-black  salt 
formed  is  converted  into  the  free  base  by  a  weak  alkaline  bath 
(soda,  soap,  or  chalk) . 

It  is  merely  a  matter  of  conjecture  at  present  if  the  black 
produced  on  the  fibre  is  identical  with  the  products  examined  in 
the  free  state. 

The  conditions  employed  in  black-printing  differ  considerably 
from  those  when  the  compound  is  prepared  in  substance;  for  ex- 
ample, the  formation  of  black  from  aniline  salts,  chlorates,  and 
metallic  salts  only  takes  place  in  presence  of  a  considerable  excess 
of  acid.  In  printing,  on  the  other  hand,  an  excess  is  avoided, 
as  it  would  tend  to  injure  the  fibre  during  the  ageing  process,  and 
besides  would  form  the  black  in  the  liquid  printing-mixture. 

For  this  reason  an  excess  of  aniline  is  generally  used,  and  in 
addition  a  part  of  the  aniline  hydrochloride  may  be  replaced  by 
the  tartrate. 

Such  a  mixture  does  not  form  black  even  on  long  standing; 
this  first  takes  place  when  the  mass  has  somewhat  dried  on  the 
fibre. 

In  general  the  oxidation  appears  to  go  further  than  when 
working  in  solution. 

The  black  prepared  in  substance  is  converted  into  dark  green 
salts  by  acids,  and  this  property  is  often  a  serious  drawback  to 
the  black  on  fibres.  This  "  greening/'  as  it  is  called,  is  produced 


ANILINE  BLACK.  199 

on  the  goods  by  acid  vapours,  for  example,  by  the  sulphurous  acid 
produced  by  the  combustion  of  coal-gas  in  work-rooms. 

This  greening  may  be  avoided  01%  at  any  rate,  reduced  to  a 
minimum,  by  energetic  oxidation.  The  compounds  produced  in 
this  manner  are  certainly  different  from  the  one  described,  and 
are  probably  its  higher  oxidation  or  chlorination  products. 

Sometimes  the  goods  are  submitted  to  a  subsequent  treatment 
to  prevent  greening.  This  may  consist  in  passing  through  a  bath 
of  bichromate  (formation  of  aniline-black  chromate)  or  of  dilute 
bleaching-powder. 

Aniline  black  dyed  on  fibres  is  one  of  the  fastest  colours.  It  is 
stable  against  soap,  is  only  slightly  attacked  by  light  and  air,  and 
is  capable  of  withstanding  a  slight  treatment  with  chlorine. 
More  chlorine  turns  it  reddish  brown. 


200  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


CHAPTER  IX. 


INDULINES  AND  NIGROSINES. 

THE  dyestuffs  included  in  this  classification  comprise  a  series  of 
colouring-matters  produced  by  action  of  azo-,  nitro-,  and  nitroso- 
compounds  on  aromatic  amines.  They  comprise  a  great  variety  of 
shades,  from  red  through  blue  to  almost  black. 

The  indulines  are  formed  in  a  great  number  of  reactions. 
Nearly  all  azo-,  azoxy-,  and  amidoazo- compounds,  if  heated  with 
salts  of  aniline  or  other  aromatic  amines,  produce  indulines,  and 
the  dyestuffs  formed  on  oxidation  of  aromatic  amines  under 
certain  conditions  belong  in  all  probability  to  this  class.  It  is 
difficult  to  say  with  certainty  to  what  extent  the  products  of 
different  reactions  are  identical  with  one  another. 

The  nitroso-derivatives  of  secondary  aud  tertiary  aromatic 
amines  also  react  with  aniline  and  its  analogues,  producing  indu- 
lines ;  and  to  the  study  of  this  reaction  and  that  of  the  amido- 
azobenzene  process  we  owe  our  present  knowledge  of  the  compo- 
sition and  structure  of  the  indulines.  Researches  in  this  direction 
have  been  made  by  Caro  and  Dale  [21],  Martius  and  Griess  [22], 
Hofmann  and  Geyger  [23],  and  Fischer  and  Hepp  [35]. 

The  lower  members  of  the  induline  series  are  soluble  in  water, 
the  higher  ones  in  alcohol. 

The  nigrosines  comprise  that  section  of  these  dyestuffs  produced 
by  action  of  nitro-compounds  on  aniline  hydrochloride  in  presence 
of  ferrous  chloride.  The  method  employed  technically  for  pro- 
duction of  indulines  consists  in  heating  aniline  hydrochloride  with 
amidoazobenzene.  If  the  reaction  be  carried  out  at  a  low  tempe- 
rature, and  especially  if  the  mixture  contains  an  excess  of  aniline 
hydrochloride,  soluble  indulines  are  produced  in  larger  quantity, 


INDULINES  AND  NIGROSINES.  201 

while  with  a  protracted  reaction  insoluble  indulines,  generally  of 
bluer  shade,  are  formed. 

Induline  C18H13N3  is  formed  by  heating  an  amidoazobenzene 
melt  for  10  minutes  at  140°.  Another  induline,  C24H18N4,  is  also 
formed  (see  below),  and  is  separated  by  the  less  solubility  of  its 
acetate  in  water. 

The  base,  C18H13N3,  forms  needles  with  a  green  metallic  lustre, 
M.P.  135° ;  the  salts  are  easily  soluble  in  water  and  dye  reddish- 
violet  shades. 

The  indulines  are  derivatives  of  phenazine;  the  simplest  has  the 
constitution : — 

XN^ 
II6"    ^NX          =  C18H13N3. 

NH        C6H5 

From  this  the  higher  indulines  are  formed  by  introduction  of 
anilido-groups,  by  phenylation,  and  by  introduction  of  the  rest  of 
paraphenylenediamine.  This  latter  reaction  always  takes  place  in 
a  normal  induline  melt,  the  paraphenylenediamine  being  formed 
from  decomposition  of  amidoazobenzene. 

Induline  C24H18N4  [36]  is  produced  by  operating  in  a  manner 
similar  to  above,  the  temperature  of  the  melt  being  about  150°. 
The  melt  is  extracted  with  a  solution  of  acetate  of  soda  under 
pressure,  whereby  the  induline,  C24H18N4,  goes  into  solution,  and 
the  free  base  precipitated  by  an  alkali.  The  base  forms  lustrous 
leaflets  soluble  in  alcohol  with  magenta-red  colour.  The  hydro- 
chloride  forms  bronzy  crystals  soluble  in  warm  water  with  a 
bluish- violet  colour.  It  dyes  bluish-violet  shades. 

Azophenine,  C30H24N4,  is  a  constant  product  of  the  induline  melt 
and  plays  an  important  part,  especially  in  the  production  of  higher 
indulines.  It  is  formed  also  by  the  action  of  various  nitroso- 
compounds  on  aniline  and  aniline  hydrochloride,  the  best  result 
being  obtained  by  paranitrosodiphenylamine.  It  may  be  produced 
synthetically  by  action  of  aniline  on  dianilidoquinone.  This 
synthesis  and  the  production  of  dianilidoquinone  on  heating  azo- 
phenine  with  sulphuric  acid  explains  its  constitution,  which  is 
that  of  a  dianilidoquinonedianil : 


202  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

N.C6H, 

1  ATM 

an, 


NH  .  C6H5 


Nil  .  C6H5' 
N.C6H5 

Azophenine  forms  red  leaflets,  M.P.  240°,  which  are  insoluble 
in  alcohol  and  ether,  but  soluble  in  aniline,  benzene,  and  toluene 
[27,  28].  On  heating  the  melt  containing  azophenine,  other 
indulines  are  formed,  amongst  which  the  following,  investigated 
by  Witt  and  Thomas,  may  be  mentioned  :  — 

Induline  B,  C18H15N3,  Azodiphenyl  blue. 

Induline  3  B,  C3oH23N5.  The  hydrochloride  is  sparingly  soluble 
in  alcohol. 

Induline  6  B,  C36H27N5.  This  is  the  best  characterised  of  the 
iriduline  series.  Its  hydrochloride  forms  well-defined  crystals 
which  are  insoluble  in  alcohol.  Its  sulphonic  acid  dyes  wool  a 
pure  blue  shade.  This  induline  is  probably  a  phenazine  produced 
by  action  of  aniline  on  azophenine  according  to  the  equation  [37]  : 

-NC6H5 
~ 


-NC6H5  C6H5N 

C6H5 

According  to  Wichelhaus  and  v.  Dechend  induline  B  is  also 
formed  by  action  of  nitrobenzene  on  aniline  hydrochloride,  a  reac- 
tion also  observed  by  Staedeler.  An  interesting  method  of  obtaining 
this  body  is  by  heating  the  aniline  salt  of  phenylamidobenzene- 
sulphonic  acid  (Tropaolin  OO).  In  this  case  sulphanilic  acid 
splits  off.  Azodiphenyl  blue  is  also  obtained  by  action  of  azoxy- 
benzene  on  aniline  hydrochloride  [24]  . 

According  to  Wichelhaus  and  v.  Dechend  a  new  colour-base  — 
Triphenylenediamine,  C18H12N2  —  is  formed  on  heating  the  hydro- 
chloride  of  azodiphenyl  blue  to  230°  [24]  . 

On  a  large  scale  the  indulines  are  prepared  by  heating  a  mixture 
of  amidoazobenzene,  aniline  hydrochloride,  and  free  aniline  to  the 
boiling-point  of  the  latter.  Reddish-violet  compounds  are  first 
formed  which  gradually  change  to  blue. 

The  first  products  of  the  reaction  are  simple  soluble  indulines 
and  azophenine,  and  from  these  the  higher  products  are  formed  by 
pheiiylation.  la  all  probability  commercial  induline  contains  a 


INDULINES  AND  NJGROSINES.  203 

mixture  of  dyestuflfs.      Paraphenylenediamine  and  diplienylamine 
are  formed  as  bye-products  in  the  induline  melt. 

According  to  Caro  a  soluble  induline  is  formed  by  heating 
amidoazobenzene  hydrochloride  with  neutral  aniline  hydrochloride 
to  100°  with  a  little  water  [29] .  This  induline  may  be  fixed  on 
tannined  cotton. 

An  apparently  different  soluble  induline  is  described  by  Istel  as 
being  formed  on  heating  2|  parts  aniline  hydrochloride,,  1  part  of 
amidoazobenzene  chloride,  and  6  parts  of  water  to  70°— 80°  C.  for 
twenty-four  hours.  The  new  dyestuff  gives  a  blue  solution  with 
water,  and  exhibits  a  reddish-brown  fluorescence.  It  dyes  on 
tannined  cotton,  and  may  be  also  fixed  on  unmordanted  cotton 
from  a  bath  containing  common  salt  or  acetate  of  soda.  The 
shades  on  tannined  cotton  are  very  fast  to  light  [38] . 

Indulines  have  also  been  prepared  technically  by  heating  azo- 
benzene  with  aniline  hydrochloride  [25] . 

Recently  a  number  of  patents  for  the  production  of  soluble 
indulines  have  been  published.  These  are  based  for  the  greater 
number  on  the  substitution  of  a  diamine,  generally  paraphenylene- 
diamine,,  for  the  aniline  in  the  usual  induline  melts.  A  short 
summary  only  of  these  processes  can  be  given  here.  The  most 
important  of  these  consists  in  heating  amidoazobenzene  hydro- 
chloride  with  paraphenylenediamine  to  180°  for  three  or  four 
hours.  A  similar  product  is  obtained  with  amidoazotoluene. 
The  dyestuffs  obtained  by  this  process  have  found  technical  appli- 
cation, and  are  known  in  commerce  as  Paraphenylene  Blues 
[39,  40]. 

Metaphenylenediamine  may  also  be  used,  but  the  products  are 
not  so  fast  to  light.  Triamidoazobenzenes  (Bismark  brown)  and 
Chrysoidine  give  soluble  indulines  on  heating  with  paraphenylene- 
diamine. 

Soluble  indulines  are  also  obtained  : — (1)  By  heating  spirit- 
soluble  indulines,,  azophenine_,  quinone,  chloranil,  azobenzene,  azo- 
toluene,  or  oxyazobenzene  with  paradiamines  (Poirrier) .  (2) 
By  heating  diamidoazoxybenzene  with  aniline  and  aniline  hydro- 
chloride.  (3)  By  heating  nitro-derivatives  of  the  amines  with 
aniline  &c.  in  presence  of  ferrous  chloride.  (4)  By  heating  the 
azo-derivatives  of  naphthylenediamine  [1,  5]  with  paraphenylene- 
diamine and  benzoic  acid. 


204  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

The  nigrosines  are  prepared  by  heating  a  mixture  of  nitrobenzene, 
aniline,  hydrochloric  acid,  and  iron  filings  to  180°-220°.  The 
colour  of  the  mixture  changes  through  reddish  violet  to  deep 
blue.  They  are  also  prepared  by  heating  a  mixture  of  crude 
nitrophenol  (mixture  of  ortho  and  para)  with  aniline  hydrochloride 
and  iron  filings.  The  nigrosines  possess  a  more  greyish  shade 
than  the  indulines,  but  it  is  not  known  with  certainty  if  the 
colouring-matters  are  different.  A  series  of  similar  products  to 
the  nigrosines  and  indulines  are  formed  by  oxidation  of  pure 
aniline  with  arsenic  acid,  but  the  exact  relationship  of  these  dye- 
stuffs  one  to  another  is  unknown.  G.  Wolf  [31]  has  published  a 
series  of  formulae  for  these  bodies,  which  cannot,  however,  be 
looked  upon  as  trustworthy,  as  the  necessary  analytical  data  are 
not  given. 

The  violet  dyestuffs  of  magenta  residues  differ  from  the  indu- 
lines in  so  far  that  they  give  a  brown  solution  with  sulphuric  acid, 
while  all  the  latter  give  a  blue. 

Sulphonic  acids  of  the  indulines  and  nigrosines  are  also  known. 

The  sodium  salts  of  the  sulphonic  acids  of  various  indulines 
come  into  commerce  under  the  names  of  Fast  Blues,  Blackley  Blue, 
Indigo  substitute,  &c.  The  difference  of  the  various  marks  depends 
on  the  shade  of  the  induline  sulphonated  and  the  number  of  sulpho- 
groups  introduced. 

The  indulines  are  mostly  insoluble  in  water  both  in  form  of 
bases  and  salts,  but  are  soluble  in  alcohol.  The  solutions  of  the 
bases  are  red  to  reddish  violet,  the  salts  are  bluish  violet,  blue,  or 
bluish  grey.  They  are  soluble  in  concentrated  sulphuric  acid  with 
a  pure  blue  colour,  the  sulpho-acids  have  the  same  colour  as  the 
salts  of  the  original  induline,  and  the  salts  of  the  sulpho-acids  have 
the  same  colour  as  the  free  bases. 

The  indulines  are  destroyed  on  oxidation,  quinone  being  formed  ; 
reducing  agents  produce  easily  oxidisable  leuco-compounds. 

The  nigrosines  have  similar  properties. 

Spirit-soluble  indulines  and  nigrosines  are  employed  as  hydro- 
chlorides,  and  are  principally  used  for  colouring  varnishes.  Spirit- 
soluble  indulines  are  applied  in  printing  by  a  peculiar  process. 
They  are  printed  in  combination  with  tannin  and  the  acetic  ethers 
of  glycerine  (monoacetine,  diacetine)  ;  on  steaming,  these  ethers 
are  decomposed,  and  the  liberated  glycerine  effects  the  combination 


TNDULINES  AND  N1GROSINES.  205 

of  the  induline  with  the  tannin  and  the  tannin  lake  with  the  fibre 
(Acetine  blue). 

Another  process  for  printing  consists  in  the  application  of  a 
mixture  of  induline  and  levulinic  acid  along  with  tannic  acid, 
the  colour  being  fixed  by  steaming  [41]. 

The  soluble  (sulphonated)  indulines  are  dyed  on  cotton  mor- 
danted with  tannin  and  tartar  emetic,  a  considerable  amount  of 
alum  being  added  to  the  dye-bath.  Wool  may  be  dyed  directly 
from  an  acid  bath,,  the  induline  generally  being  used  in  combina- 
tion with  other  acid  colours.  Silk  is  dyed  in  a  bath  containing 
boiled -off  liquor,  the  shades  being  brightened  by  addition  of  sul- 
phuric acid. 

Soluble  indulines  of  the  unsulphonated  class  are  basic  dyestuffs, 
and  are  principally  used  in  cotton-dyeing  on  a  mordant  of  tannic 
acid  and  tartar  emetic. 


Ilosindulines  [42.  43,  44]. 

These  dyestuffs  are  indulines  of  the  naphthalene  and  benzene- 
naphthalene  series. 

Nitrosoethyl  and  nitrosophenylnaphthylamine,  if  heated  with 
aniline,  produce  a  deep-red  dyestuff,  and  an  analogous  compound 
is  obtained  by  heating  naphthoquinone  and  certain  of  its  deriva- 
tives with  aniline  and  aniline  hydrochloride.  The  latter  dyestuff 
yields  sulphonic  acids  which  dye  animal  fibres  brilliant  bluish  or 
brownish-red  shades.  The  sodium  salt  of  one  of  these  acids  is 
known  as  Azocarmine.  The  rosinduline  from  nitrosophenyl  and 
naphthylamine  and  aniline  has  the  composition  C38H19N3.  It  forms 
red  monoacid  and  green  diacid  salts,  the  latter  are  decomposed  by 
water.  Hydrochloride,  (C28H18N3HC1)2  -fl£H2O,  reddish-brown 
prisms  soluble  in  water  and  alcohol.  Sulphate,  C28H19N3H2SO4-|- 
H2O.  The  constitution  of  the  base  may  be  expressed  by  the 
formula  : 


C«H, 


206 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


Fluorindines. 

These  comprise  a  series  of  weak  dyestuffs  discovered  by  Caro 
and  Witt,  the  type  of  which  is  obtained  by  heating  azophenine 
with  concentrated  sulphuric  acid  or  with  zinc  powder.  The  for- 
mation of  this  compound,  which  contains  two  azine  rings,  may  be 
represented  by  the  following  equation  : — 
C6H5NH\n  „  /NC6H5 


Fluorindines  are  also  produced  by  heating  orthodiamines  and 
by  heating  a  mixture  of  diamidoplienazine  and  orthophenylene- 
diamine  [45] . 

The  fluorindines  are  blue  or  violet  compounds.  In  sulphuric 
acid  or  alcoholic  solution  they  exhibit  a  magnificent  brick-red 
fluorescence  which  is  very  characteristic. 


QUINOLINE  AND  ACRIDINE  DYESTUFFS. 


207 


CHAPTER  X. 


QUINOLINE  AND  ACRIDINE  DYESTUITS. 

QUINOLINE  and  Acridine  and  their  homologues  belong  to  the 
chromogens.  The  chromogen  character  is  but  slight,  and  is  only 
inconsiderably  developed  by  introduction  of  amido-groups.  The 
simple  amido  bases  form  yellow  salts,,  which  are,,  however,  not 
dyestuffs.  These  are  formed,  however,  by  introduction  of  an 
amidated  benzene  residue. 

This  is  the  case  with  flavaniline  and   chrysaniline,  which  are 
derivatives  of  phenylquinoline  and  phenylacridine  respectively- — 


CGH4NH2 


XH.; 


N 
Flavaniline. 


0 

06H4NII2 

Chrysaniline. 


Another  class  of  dyestuffs  is  known  in  which  quinoline  does  not 
appear  to  be  the  real  chromogen.  The  fact  that  these  bodies 
cannot  be  obtained  from  pure  quinoline,  but  only  in  presence  of 
its  homologues,  gives  reason  for  the  assumption  that  they  are 
analogous  to  the  phenylmethane  dyestuffs,  and  that  a  methane 
carbon  atom  links  together  several  quinoline  rings. 

These  dyestuffs  include  the  cyanines,  quinoline  red,  and  pro- 
bably quinoline  yellow  (?). 


208  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Cyanine  [2,  3,  4,  5]. 

On  heating  a  mixture  of  quinoline  and  lepidine  (rnethylquino- 
line)  [4]  with  an  alkyl  iodide  in  presence  of  an  alkali,  a  blue  dye- 
stuff  is  formed,  which  contains  one  molecule  of  each  of  the  bases 
and  the  alcohol  radical  used  twice.  It  is  also  formed  by  treating 
a  mixture  of  the  alkyl  iodide  compounds  of  quinoline  and  lepidine 
with  alkali  [4] .  One  molecule  of  hydriodic  acid  is  split  off  and 
the  iodide  of  cyanine  formed. 

The  cyanines  are  strongly  basic  compounds  ;  the  iodine  can 
only  be  removed  from  the  iodides  by  silver  oxide. 

The  monoacid  salts  are  crystalline  and  of  a  beautiful  blue 
colour.  With  weak  acids,  often  even  with  carbonic  acid,  they  are 
converted  into  the  colourless  di-acid  salts  [2,  5]. 

The  cyanines  dye  blue  shades,  which  are,  however,  too  sensitive 
to  light  and  acids  to  be  of  practical  value. 

Dimethylcyanine  [4]. — The  iodide  C2iH19N2I  is  formed  from  the 
methyl  iodides  of  quinoline  and  lepidine.  It  forms  lustrous 
green  needles,  M.P.  291°.  Its  blue  solution  is  decolorised  by 
carbonic  acid.  The  ethyl  iodides  of  the  above  bases  form  the  corre- 
sponding cyanine  iodide  C^R^Ngl. 

An  isomeric  cyanine  is  formed  if  quinaldine  is  used  in  place  of 
lepidine  [4]. 

Isoamylcyanine,  discovered  by  Greville  Williams  [5]  and  ex- 
amined later  by  Hofmann  [2],  is  best  known.  According  to  Hof- 
mann  it  is  formed  from  pure  lepidine  and  possesses  the  composition 
C3oH39N2I.  In  all  these  iodides  the  iodine  may  be  replaced  by 
other  acid  radicals. 

It  is  possible  that  the  cyanines  are  constituted  similarly  to  the 
phenylmethane  dyestuffs.,  the  methyl  group  of  the  lepidine  fur- 
nishing the  methane  carbon  atom.  The  cyanines  belong  to  the 
earliest  artificial  dyestuffs,  the  first  representative  having  been 
discovered  by  Greville  Williams  in  1856. 


Qiimoline  Red 

is  obtained  by  action  of  benzo-trichloride  on  coal-tar  quinoline  in 
presence  of  zinc  chloride  [1,  6].  According  to  Hofmann's  re- 
searches there  are  two  different  dyestuffs  of  this  class,  one  of 


QUINOLINE  AND  ACRIDINE  DYESTUFFS.  209 

which  is  derived  from  quinoline  and  quinaldine  and  the  other  from 
quinaldine  and  isoquinoline. 

The  isoquinoline  derivative  is  easier  to  prepare  and  a  far  better 
yield  is  obtained. 

The  quinoline  red  from  isoquinoline  has  the  composition 
C26H18N2.  It  is  a  base  and  forms  a  hydrochloride  of  the  formula 
C26H18N2HC1.  It  crystallises  in  thin  quadratic  leaflets  or  in 
larger  prisms.  It  is  sparingly  soluble  in  cold  water,  easily  in  hot, 
and  is  separated  again  by  an  excess  of  hydrochloric  acid. 

The  platinum  double  salt  has  the  formula  (C26H19N2C1)2  PtCl4. 

On  heating  quinoline  red  with  ammonium  sulphide,  benzyl  mer- 
captan  is  split  off,  and  a  compound  of  the  composition  C19H14N2 
is  formed. 

On  dry  distillation  it  yields  a  base  of  the  composition  C17H15N. 

Quinoline  red  may  be  regarded  as  analogous  in  constitution  to 
the  tripheiiy  1m ethane  dyestuffs,  the  methane  carbon  atom  of  the 
benzotrichloride  entering  into  two  quinoline  residues. 

It  gives  a  magnificent  eosine-red  shade  on  silk,  and  exhibits  a 
fluorescence  which  surpasses  that  of  every  other  dyestuff.  The 
shades  are,  however,  extremely  sensitive  to  light. 


Quinoline  Yellow  (QUDSTOPHTHALON)  [1,  6]. 
C18HnN02. 

Is  formed  by  action  of  phthalic  anhydride  on  quinaldine  or  on 
coal-tar  quinoline  containing  quinaldine  in  presence  of  zinc 
chloride.  Quinoline  yellow  crystallises  from  alcohol  in  fine  yellow 
needles,  M.P.  235°.  It  is  insoluble  in  water  and  ether,  pretty 
easily  soluble  in  hot  alcohol  and  glacial  acetic  acid,  and  easily  in 
strong  sulphuric  acid.  It  has  no  basic  properties  and  dyes  wool 
and  silk  yellow.  Its  sulphonic  acid,  obtained  by  treating  with 
fuming  sulphuric  acid,  dyes  wool  and  silk  pure  yellow  like  picric 
acid.  Basic  dyestuffs  may  be  obtained  by  heating  with  ammonia 
under  pressure.  Probably  these  are  formed  by  substitution  of 
oxygen  by  nitrogenous  groups. 

The  homologues  of  quinaldine  yield  similar  dyestuffs  with 
phthalic  anhydride  [7]. 

A  similar  dyestuff,  pyrophthalon,  of  the  composition  C14H9NO2, 
is  obtained  from  coal-tar  picoline  and  phthalic  anhydride  [7] . 

p 


210  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

In  all  these  reactions,  phtlialic  anhydride  may  be  replaced  by 
the  anhydrides  of  the  chlorinated  phthalic  acids. 

Owing  to  its  high  price  quinoline  yellow  has  only  found  a  limited 
application.  It  gives  very  fast  shades,  and  would  be  valuable  in 
dyeing  if  the  cost  of  production  were  less.  It  is  applied  solely  as 
sulphonic  acid  and  is  dyed  like  the  acid  dyestuffs.  The  shades 
produced  are  pure  yellow,  free  from  any  tinge  of  red. 


Fara^midophenyl-y-lepidine  (Flavaniline)  [8,  9, 10]. 

C16H14N2. 

This  dyestuff  is  prepared  by  heating  acetanilide  with  zinc 
chloride  to  250°-270°.  The  melt  is  extracted  with  hydrochloric 
acid,  and  the  flavaniline  precipitated  by  addition  of  salt  and  acetate 
of  soda.  The  yield  is  very  small. 

Flavaniline  is  a  strong  base  ;  it  forms  long  colourless  needles, 
sparingly  soluble  in  water,  easily  in  alcohol  and  benzene,  M.P.  97°. 
It  may  be  distilled  without  decomposition.  The  monoacid  salts 
of  flavaniline  dye  wool  and  silk  pretty  pure  yellow  shades. 

Hydro  chloride,  C16H14N2,HC1,  forms  yellowish-red  prisms  with 
a  bluish-red  reflex.  It  is  easily  soluble  in  water. 

Dihydrochloride,  C16H14N2,(HC1)2,  is  a  white  salt  obtained  by 
adding  concentrated  hydrochloric  acid  to  the  aqueous  solution  of 
the  former.     It  is  decomposed  by  water  or  on  heating. 
C16H14N22HCl,PtCl4  forms  a  yellow  crystalline  precipitate. 
Ethyl  flavaniline  is  obtained  by  action  of  ethyl  iodide  on  an 
alcoholic  solution  of  the  base. 

Iodide,  C16H13N2(C2H5)HI,  forms  long  ruby-red  needles. 
Flavaniline  contains  an  amido-group,  and  forms  a  diazo-com- 
pound  which  is  converted  into  flavenol,  C16H13NO,  on  boiling  with 
water.  This  compound  exhibits  weak  basic  and  acid  properties. 
It  forms  colourless  leaflets,  which  may  be  sublimed  with  partial 
decomposition,  M.P.  128°.  It  forms  colourless  salts  with  acids. 
On  distilling  with  zinc  powder  it  yields  a  new  base — flavoline, 
C16H13N3.  This  latter  compound  forms  colourless  lustrous  crystals, 
M.P.  65°.  It  yields  monoacid  salts. 

The  behaviour  of  flavolinc  on  oxidation  shows  it  to  belong  to 
the  quinoline  series.  By  oxidation  with  permanganate  it  yields 
first  lepidine  carbonic  acid, 


QUINOLIXE  AND  AC1UDINE   DYESTUFFS. 


211 


COOH 

on  further  oxidation  picoline  trioarbonic  acid, 

C5HN(COOH)3, 


and  finally  pyridine  tetracarboiiic  acid,  C5NH(COOH)4. 
These  facts  show  that  flavoline  is  a  methylpheiiylquinoline 

CPI, 


-C6H5 


Flavenol  is  therefore  an  hydroxyl-  and  flavaniline  an  amiilo- 
derivative  of  this  compound.  The  constitution  of  flavaniline  is 
expressed  by  the  formula  : 


An  interesting  synthesis  of  flavaniline  was  effected  by  O. 
Fischer.  It  consists  in  the  condensation  of  equal  molecules  of 
ortho-  and  para-amidoacetophenone,  according  to  the  equation  : 


XII, 


+H.O 


21.2  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Probably  the  formation  of  flavaniline  from  acetanilicle  and 
zinc  chloride  is  due  to  a  molecular  change  of  the  acetanilide 
to  the  isomeric  amidoacetophenones,  which  then  form  flavaniline. 


Berlerine. 
C20H17N04. 

Berberine  is  an  alkaloid  occurring  in  many  plants,  and  be- 
longs to  the  quinoline  dyestuffs.  So  far  as  our  present  know- 
ledge reaches,  it  is  the  only  member  of  this  series  occurring  in 
nature,  and  is  also  the  only  natural  dyestuff  with  basic  properties 
capable  of  being  fixed  on  fibres  like  basic  aniline  dyes. 

Berberine  has  been  found  in  many  plants.  The  largest  quan- 
tities are  found  in  Calumba  roots  (Cocculw  palmatus)  [19],  and  in 
the  roots  of  Berberis  vulgaris,  Linn.  [20].  The  latter  is  the 
only  one  of  importance  in  dyeing. 

Pure  berberine  forms  yellow  needles,  sparingly  soluble  in 
alcohol  and  in  water.  It  loses  water  of  crystallisation  at  100° 
and  melts  at  120°.  It  is  a  monoacid  base  forming  soluble  crystal- 
line salts  with  acids.  The  nitrate  C20H17NO4,HNO3  is  especially 
noteworthy  for  the  ease  with  which  it  forms  large  crystals;  it  is 
insoluble  in  excess  of  nitric  acid.  Berberine  is  capable  of  forming 
lakes  with  metallic  oxides.  The  dry  hydrochloride  is  turned  red 
by  chlorine.  On  melting  with  potash  it  yields  quinoline  and  two 
acids,  one  of  which,  C8H8O4,  appears  to  be  homologous  with 
proto-catechuic  acid  [16].  On  oxidation  with  nitric  acid, 
berberine  gives  pyridine  tricarbonic  acid  [17,  18]. 

Reducing  agents  convert  berberine  to  colourless  hydro-berberine, 
C20H21N04  [16]. 

In  dyeing,  berberine  is  used  in  form  of  a  decoction  of  the 
berberis  roots.  On  animal  fibres  it  is  dyed  from  a  neutral  bath, 
and  On  cotton  it  is  fixed  with  tannic  acid.  It  is  almost  exclusively 
used  for  dyeing  leather. 

Chrysanilines. 

C19H15N3  and  C20H17N3. 

The  chrysanilines  are  formed  in  small  quantities  as  bye-products 
in  the  manufacture  of  magenta,  both  by  the  arsenic  acid  and  the 


QUINOLINE  AND  ACRIDINE  DYESTUFFS.  213 

nitrobenzene  processes.  They  are  separated  from  the  first  magenta 
mother-liquors  by  partial  precipitation  with  soda,  and  are  finally 
crystallised  from  pretty  strong  nitric  acid.  The  chrysaniliiie 
examined  by  Hofmann  [11]  has  without  doubt  the  formula 
C2oH17N3 ;  bnt  recent  researches  by  Fischer  and  Koerner  [12] 
render  it  probable  that  crude  chrysaniline  contains  two  homo- 
logous bases,  C19H15N3  and  C20H17N3.  At  least  the  analytical 
results  obtained  by  Hofmann  cannot  be  brought  in  unison  with 
the  formula  C19H15Na  set  up  by  the  latter  chemists. 

The  chrysaniline  C2oH17N3  [11],  when  precipitated  from  its 
salts  by  alkali,  forms  a  light  yellow  powder  similar  to  precipitated 
lead  chromate.  It  is  almost  insoluble  in  water,  dissolves  easily  in 
alcohol,  benzene,  and  ether.  The  two  latter  solutions  exhibit  a 
beautiful  yellow-green  fluorescence.  The  base  may  be  distilled 
with  partial  decomposition.  Chrysaniline  forms  two  series  of 
salts  with  acids,  both  of  which  are  yellow  to  orange  in  colour. 
With  the  exception  of  the  picrate  and  the  hydriodide,  the  salts 
are  soluble  in  water,  but  sparingly  soluble  in  an  excess  of  acid. 
On  dilution,  the  diacid  salts  are  split  up  into  monoacid  sale  and 
water. 

Nitrate,  C2oH17N8,HNO3,  forms  orange-yellow  needles,  sparingly 
soluble  in  cold  water,  easily  in  hot.  From  the  solution,  nitric 
acid  precipitates  the  diacid  nitrate,  C20H17N3,2HNO3,  in  orange- 
yellow  clusters  of  needles.  Chrysaniline  is  capable  of  with- 
standing the  action  of  pretty  strong  nitric  acid. 

If  impure  chrysaniline  is  dissolved  in  strong  nitric  acid,  the 
nitrate  crystallises  out  on  standing,  and  this  property  is  utilised  in 
the  purification  of  the  dyestuff. 

The  hydrochlorides,  C20H17N3,HC1  and  C20H17N3,2HC1,  are 
more  easily  soluble  than  the  corresponding  nitrates. 

Picrate,  C20H17N32(C6H2(NO2)3OH)  +  H2O,  forms  red  needles 
insoluble  in  water  and  sparingly  soluble  in  alcohol. 

Trimethylchrysaniline,  C20H14(CH3)3N3.  The  dihydriodide, 
C20HU(CH3)3N3(HI)2,  is  formed  by  heating  chrysaniline,  methyl 
iodide,  and  methyl  alcohol  to  100°  for  five  hours.  It  forms  orange- 
red  needles,  soluble  in  hot  water.  On  adding  ammonia  to  the 
hot  solution,  the  mono-hydriodide  separates  in  yellow  needles. 
The  base  may  be  obtained  from  these  iodides  by  action  of  silver 
oxide.  It  forms  easily  soluble  salts  with  most  acids. 

C20H14(CH3)3N3(HCl)2,PtCl4  forms  yellow  felted  needles. 


214 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


The  corresponding  ethyl  derivatives  may  be  obtained  in  an 
analogous  manner  by  the  action  of  ethyl  iodide.  Amyl  derivatives 
have  also  been  prepared  [11]. 

Chrysaniline  C19H15N3  [12]  was  obtained  by  Fischer  and 
Koerner  from  commercial  chrysamline.  The  base  crystallises 
from  benzene  in  clusters  of  golden-yellow  needles,  containing  one 
molecule  of  benzene,  which  is  expelled  on  drying.  It  melts  at 
upwards  of  200°,,  and  distils  \vith  partial  decomposition. 

Chrysophenol  C19H13N2O  [12]  is  formed  by  heating  the  above 
compound  with  concentrated  hydrochloric  acid  to  180°. 

It  forms  small  orange  needles,  forming  salts  with  acids,  and  also 
reacting  like  a  weak  acid  towards  alkalies.  It  dissolves  in  soda, 
forming  a  light  yellow  solution  from  which  acids  precipitate  it  as 
an  orange  precipitate. 

On  heating  with  acetic  anhydride,  chrysamline  yields  a  diacetyl 
compound  [13],  C1j>H13N3(C2H3O)2,  which  still  possesses  basic 
properties,  forming  monoacid  salts  with  acids. 

C19H13Ns(C2HtHO)2HCl  forms  long  yellow  needles,  easily  soluble 
in  water  [13]. 

The  corresponding  nitrate  is  sparingly  soluble. 

By  treating  chrysaniline,  C19H15N3,  with  nitrous  acid,  two 
nitrogen  atoms  are  converted  into  diazo-groups.  On  boiling  the 
resulting  diazo-compound  with  alcohol,  phenylacridine  is  formed  : 

N 
C6H4      |       C6H4. 


C6H5 

It  follows  therefore  that  chrysaniline  is  a  diamidophenylacri- 
dine  [12]. 

An  interesting  synthesis  of  chrysaniline  was  effected  by  Fischer 
and  Koerner  [12]. 

Orthonitrobenzaldehyde  condenses  with  aniline  to  form  ortho- 
nitroparadiamido-triphenylmethane,  which  on  reduction  yields 
orthodiparatriamido-triphenylmethane  : 


QUINOLINE  AND  ACRIDIXE  DYESTUFFS. 


215 


NH2 

This  compound  yields  chrysaniline  on  oxidation. 

As  in  the  formation  of  acridine  the  nitrogen  and  carbon 
atoms  take  up  ortho  positions  in  both  benzene-nuclei,  chrysaniline 
has  the  following:  constitution  : 


-XH, 


For  a  considerable  period  chrysaniline  was  the  only  basic 
yellow  dyestuff,  and  for  this  reason  was  largely  used  in  cotton- 
dying.  Wool  and  silk  are  dyed  directly,  cotton  requires  a  tannin 
mordant.  The  shade  produced  is  an  orange-yellow,  noteworthy 
for  its  fastness  to  light. 


216  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

At  present  chrysaniline,  which  is  used  as  nitrate  or  hydro- 
chloride,,  under  the  name  of  Phosphine,  has  but  a  limited  applica- 
tion in  silk  and  cotton-dyeing. 

The  reason  for  this  is  that  there  is  no  good  method  for  pro- 
duction of  phosphine,  and  as  its  preparation  from  magenta- 
residues  is  somewhat  complicated,  its  price  is  relatively  high. 


Acridine  Yellow  [22]. 

This  dyestuff  is  a  hydrochloride  of  diamidodimethylacridine  of 
the  constitution : 


For  its  preparation  formaldehyde  is  condensed  with  metatoluy- 
lenediamine,  and  the  resulting  body  treated  with  acid,  ammonia 
splits  off,  and  the  resulting  leuco-base  is  oxidised.  It  dyes  silk 
yellow  with  green  fluorescence. 


Acridine  Orange. 

Acridine  orange  is  according  to  its  formation  a  tetramethyl- 
diamidoacridine : 

CH 

(CH3)2NC6H3<  |    >C6HJ5N(CH3)2, 

N 

and  is  obtained  by  heating  of  tetramethyltetramidodiphenylme- 
thane  with  acids  and  subequerit  oxidation  of  the  resulting  leuco- 
acridine.  Acridine  orange  is  a  basic  dyestuff  producing  reddish- 
orange  shades  on  cotton. 

Benzqflavine. 

A   diamidophenyldimethylacridine  isomeric   with    chrysaniline 
been  brought  into  commerce  under  the  above  name. 


QUINOLINE   AND  ACRID1XE  DYESTUFFS. 


217 


According  to  a  patent  of  C.  Oehler,  it  is  obtained  in  the 
following  manner  [21]  : — 

Metaphenylenediamine,  or  metatoluylenediamine,  is  condensed 
with  benzaldehyde,  forming  tetramidotriphenylmethane  or  its 
homologues.  The  latter  base  on  heating  with  acid  loses  one 
molecule  of  ammonia,  yielding  diamido-hydrophenylacridine,  the 
leuco-base  of  benzoflavine_,  which  is  formed  on  oxidation  : 


NII2 


Tetramidotiiphenylme  thane. 


Diamidoliydrophenylacridine. 


Benzoflavme. 


Benzoflavine  comes  into  commerce  as  a  yellow  powder.  It  is 
easily  soluble  in  hot  water,  and  the  solution  solidifies  to  a  jelly  on 
cooling.  From  the  solution  concentrated  hydrochloric  acid  pre- 


218  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

cipitates  the  sparingly  soluble  orange  hydrochloride.  The  free 
base  precipitated  by  an  alkali  forms  a  light  yellow  powder,  which 
dissolves  in  ether  with  a  beautiful  green  fluorescence,  similar  to 
that  of  chrysaniiine. 

The  dyestuff  dissolves  in  concentrated  sulphuric  acid  with  a 
light  yellow  colour,  which  becomes  orange  on  dilution. 

The  shades  produced  on  wool,  silk,  and  on  cotton  mordanted 
with  tannic  acid  resemble  those  with  auramine.  They  may  be 
distinguished  by  their  behaviour  towards  concentrated  hydro- 
chloric acid,  benzoflavine  becoming  orange,  while  auramine  is 
destroyed.  The  stability  of  benzoflavine  towards  acids  is  a  decided 
advantage,  but  it  does  not  appear  to  be  so  fast  to  light  as 
auramine. 


INDIGO  DYESTUFFS.  219 


CHAPTER  XI. 

INDIGO  DYESTUFFS. 

THE  colouring-matters  of  the  indigo  group,,  of  which  the  most 
important  is  indigo  blue,,  are  derivatives  of  indol.  This  compound 
is  closely  related  to  pyrrol,  both  as  regards  constitution  and  pro- 
perties. The  relationship  existing  between  indol  and  pyrrol  is 
analogous  to  that  of  benzene  to  naphthalene,,  or  of  pyridine  to 
quinoline,  and  is  best  shown  by  the  following  formulae  :  — 


CH—        ^v 

||  /CH       C6H4\  CH 

CII—  NH  7  X  NH-" 

"  Pyrrol.  Indol. 

The  nitrogen  and  carbon  atoms  of  the  side  ring  occupy  ortho 
positions  in  the  benzene  ring,,  and  form  with  the  third  carbon  atom 
a  closed  chain  containing  five  members  [1,  2]  . 

Indol,  like  pyrrol,  possesses  slight  basic  properties,  and  also 
colours  a  strip  of  fir,  moistened  with  acid,  red.  It  forms  colour- 
less leaflets,  M.P.  52°,  which  have  a  peculiar,  unpleasant  smell.  It 
boils  at  245°  writh  partial  decomposition.  With  nitrous  acid  it 
yields  a  nitroso-derivative.  Of  the  salts,  only  the  picrate  is  stable. 
With  acetic  anhydride  it  forms  acetylindol. 

Indol  was  first  obtained  by  reduction  of  indigo  blue.  It  is  aho 
produced  in  the  pancreatic  digestion  of  albuminoids  [2],  and  by 
melting  the  latter  with  potash. 

It  may  be  obtained  synthetically  by  heating  orthonitrocinnamic 
acid  with  potash  and  iron  filings,  and  by  passing  diethylortho- 
toluidiue  through  a  red-hot  tube. 

Indol  is  also  formed  by  melting  carbostyril  with  caustic  potash 
[7],  by  distillation  of  nitropropeiiylbenzoic  acid  with  lime  [8],  by 
heating  orthoamidostyrol  with  sodium  ethylate  [9],  by  passing 


220  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

tetrahydroquinoline  through  a  red-hot  tube  [10],  and  by  treating 
orthonitrophenylacetaldehyde  with  zinc  powder  and  ammonia  [11]  . 

A  general  synthetic  method  for  production  of  alkyl-indols  is 
that  of  Emil  Fischer. 

Ketones  react  with  phenylhydrazine  to  produce  hydrazones  : 


o. 

The  hydrazones,  on  heating  with  zinc   chloride,  split  off  one 
molecule  of  ammonia,  with  production  of  a  substituted  indol  : 


Substituted  hydrazines  yield  the  corresponding  substituted  in- 
dols  ;  for  example,  from  diphenylhydrazine  and  acetone  diphenyl- 
indol  is  formed  : 


DERIVATIVES  OP  INDOL. 
IndoxyL 

/CH. 


This  hydroxy-indol  occurs  in  the  urine  of  herbivorous  animals 
as  indoxylsulphuric  acid.  Indol  is  converted  into  indoxyl- 
sulphuric  acid  in  the  animal  organism.  From  this  compound 
indoxyl  is  formed  by  warming  with  concentrated  hydrochloric 
acid.  It  may  also  be  obtained  by  heating  indoxylic  acid,  accord- 
ing to  the  equation  : 

C9H7NO3  =  C8H7NO  +  CO2  [13]. 

Indoxyl  is  an  oil  not  volatile  in  a  current  of  steam.  On.  oxi- 
dation it  gives  indigo  blue. 

Indoxylsulphuric  acid  may  be  obtained  by  heating  indoxyl 
with  potassium  pyrosulphate  [1^].  It  exists  only  in  the  form  of 
its  salts.  These  are  colourless  and  yield  indigo  blue  on  heating 
or  on  oxidation. 


INDIGO  DYESTUFFS.  221 


Indoxylic  Acid, 

/C(OH)X 
C6H/  ,C—  COOH. 


The  ethyl  ether  of  this  acid  is  formed  by  reduction  of  orthonitro- 
phenylpropiolic  acid  ethyl  ether  with  ammonium  sulphide  [13]. 

The  free  acid  is  obtained  by  saponification  of  the  ether  with  an 
alkali.  It  forms  a  crystalline  precipitate,  sparingly  soluble  in 
water.  It  splits  up  into  indoxyl  and  carbonic  acid  on  heating. 
Oxidising  agents  convert  it  to  indigo  blue,  while  on  heating  with 
concentrated  sulphuric  acid  indigo  sulphonic  acid  is  formed. 

O.xindol  [14,  24], 


This  compound  is  an  inner  anhydride  of  orthoarnidophenyl  acetic 
acid,  and  is  isomeric  with  indoxyl.  It  is  formed  by  reduction  of 
isatin  with  sodium  amalgam  [14],  and  of  acetylorthoamidophenyl- 
glycollic  acid  with  hydriodic  acid  [15].  It  forms  colourless 
needles,  M.  P.  120°,  and  exhibits  simultaneously  basic  and  acid 
properties.  It  reacts  with  nitrous  acid,  producing  isatinoxime 


Itioxindol, 


is  the  inner  anhydride  of  orthoamidophenylgly  collie  acid.  It  is 
the  first  product  of  the  reduction  of  isatin  with  zinc  powder  [14]. 
It  forms  colourless  prisms,  M.P.  180°.  On  heating  strongly, 
aniline  is  formed.  It  oxidises  in  aqueous  solution,  forming  first 
isatyde,  and  then  isatin.  Reducing  agents  convert  it  to  oxindol. 
Dioxindole  is  a  dibasic  acid,  but  also  possesses  slight  basic  pro- 
perties. Its  acetyl  derivative  is  decomposed  by  baryta  water, 
acetylamidophenylglycollic  acid  being  formed.  It  yields  a  nitroso- 
derivative  with  nitrous  acid. 


222  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Isatin. 

>N' 

This  compound  is  the  inner  anhydride  of  orthoamidophenylgly- 
oxylic  acid  : 

/CO— COOH 

6      4-x^ 

Isatin  is  formed  by  oxidation  of  indigo  with  nitric  acid  or 
chromic  acid  [16].  It  may  also  be  obtained  by  oxidation  of 
arnido-oxindol,  and  of  carbostyril  [18],  and  by  boiling  ortho- 
nitrophenylpropiolic  acid  with  caustic-potash  solution.  Further 
methods  of  formation  are  given  under  the  synthesis  of  indigo- 
blue. 

Isatin  forms  orange  prisms,  M.P.  200°.  It  is  sparingly  soluble 
in  water,  easily  in  alcohol  and  ether.  It  possesses  the  properties 
of  a  weak  monobasic  acid,  but  also  reacts  like  the  aldehydes  and 
ketones  ;  for  example,  it  combines  with  bisulphites  of  the  alkalies, 
and  with  phenylhydrazine  arid  its  sul phonic  acids  [65]. 

By  oxidation  with  dilute  nitric  acid  it  yields  nitrosalicylic  acid, 
and  on  melting  with  caustic  potash,  aniline  is  formed.  By  oxi- 
dation with  chromic  acid  in  acetic-acid  solution  anthranilcarbonic 
acid  (Kolbe's  Isatoic  Acid)  [21]  is  produced : 

/CO 
C6H4    | 

XN— COOH 
Phosphorus  pentachloride  converts  isatin  to  isatin  chloride : 

C6H4C^     /CC1. 

Isatin  forms  a  blue  condensation-product  (indophenine)  with 
thiophene.  On  reduction  with  ammonium  sulphide,  isatide 
C16Hi2N204  [16]  is  formed.  With  zinc  powder  in  acetic-acid 
solution,  isatin  yields  hydroisatin;  by  more  energetic  reducing- 
agents  oxy-  and  dioxy-indol  are  formed.  Chlorine  and  bromine 
react  with  isatin,  forming  chlorine  and  bromine  derivatives 
respectively.  Acetic  anhydride  produces  an  acetyl  isatiii  [15], 


INDIGO  DYESTUFFS.  223 

probably  a  derivative  of  pseudo-isatin.  Isatin  cliloride  yields 
indigo  blue  on  reduction,  indigo-purpurin  being  sometimes  formed 
as  a  bye-product  [22].  Isatin  forms  ethers  with  the  alcohol  radi- 
cals. The  methyl  ether  of  isatin  yields  a  condensation-product, 
methyl  isatide,  C17H12N3O4.  Isatin  combines  with  hydroxyla- 
mine,  forming  an  oxime,  C8H6N3O2  [25],  which  is  identical  with 
the  nitroso-oxindol  discovered  by  Bayer  and  Knop  [14,  24] 
(pseudo-isatin,  see  constitution  of  the  Indigo  group). 

Isatin  is  capable  of  yielding  condensation-products  with  hydro- 
carbons [58] .  In  the  formation  of  these  bodies  one  oxygen  atom 
of  the  isatin  is  replaced  by  two  monovalent  hydrocarbon  rests. 
From  their  behaviour  these  bodies  appear  to  be  derivatives  of 
pseudo-isatin ;  the  toluene  derivative  has  accordingly  the  formula  : 

(C;H7)3 


Similar  condensation-products  may  be  obtained  with  tertiary 
bases  and  phenols.  They  yield  dyestuffs  on  oxidation,  which  pro- 
bably belong  to  the  triphenylmethane  series  [58] . 

The  compound  formed  from  isatin  and  thiophene  has  the 
formula  : 

C12H7NOS  [58]. 

Indolin,  see  62,  63. 

Isatic  Acid. 
-  /CO— COOH. 


(Orthoamidophenylglyoxylic  acid,  orthoamidobenzoylformic  acid.) 
The  salts  of  this  acid  are  formed  on  heating  isatin  with  a  stron^ 
solution  of  caustic  alkali.  The  free  acid  may  be  obtained  by  de- 
composition of  the  lead  salt  with  sulphuretted  hydrogen  [26],  or 
synthetically  by  reduction  of  orthonitrophenylglyoxylic  acid  with 
ferrous  sulphate  and  caustic  soda.  The  acid  is  unstable,  its  aqueous 
solution  decomposes  on  boiling,  isatin  and  water  being  formed. 
Acetylisatic  acid  is  formed  by  treating  acetylisatin  with  a  cold 
solution  of  a  caustic  alkali  [15], 


224  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


Isatogenic  Ether  [13,  27]. 

/CO— C.COO.CoH5 
C6H4^      /\ 
^N— O 

This  body  is  isomeric  with  the  ether  of  orthonitrophenylpropiolic 
acid,  and  is  formed  on  treating  the  latter  with  concentrated  sul- 
phuric acid.  It  forms  yellow  needles,  M.P.  115°. 


Diisatogen  [27], 
^CO— C— C—  COX 

c6H4^   /\    |\     ;:c6H4, 

^  — O     O—  ^ 

is  formed  on  treating  dinitrodiphenyldiacetylene  with  concen- 
trated sulphuric  acid.  It  forms  red  needles,  soluble  only  in 
chloroform,  nitrobenzene,  and  strong  sulphuric  acid.  It  is  easily 
converted  by  reducing  agents  to  indigo  blue. 


Indoxanthic  Ether  [28]. 
CO—  C(OH)C02C2H5. 

PR/         / 


This  compound  is  obtained  by  oxidation  of  indoxylic  ether  with 
ferric  chloride.  It  forms  straw-yellow  needles,  M.P.  107°.  Alka- 
lies convert  it  to  anthranilic  acid.  It  forms  a  nitrosamine  with 
nitrous  acid  ;  on  reduction  indoxylic  ether  is  reproduced. 


Indigo-Blue. 

C6H4— CO— C=C— CO— C6H4. 

NH  NH 

Indigo  blue  is  the  most  important,  in  fact  the  only  important 
derivative  of  indol  from  a  technical  point  of  view. 


INDIGO  DYESTUFFS.  225 

Indigo  occurs  as  a  glucoside,  indican,  in  various  plants  (Indi- 
gofera  tinctoria,  Indigofera  anilj  Polygonum  tinctorium,  and  Isatis 
tinctoria) .  According  to  Schunck  [29] ,  indican  from  Isatis  tinc- 
toria has  the  composition  C26H31NO17,  and  decomposes  according 
to  the  equation  : 

2C26H31N017  +  4H20  =  C16H10N202  +  C6H10O6. 

Indigo-blue.      Indiglucine. 

It  is,  however,  uncertain  if  the  same  indican  occurs  in  all  plants. 

In  the  industrial  preparation  of  indigo,  an  aqueous  extract  of  the 
plants  is  submitted  to  fermentation.  The  indigo  blue  produced  is 
probably  reduced  by  the  sugar,  soluble  indigo  white  being  formed. 
On  subsequent  oxidation  in  the  air,  indigo  blue  separates  mixed 
with  various  impurities.  The  crude  product  obtained  in  this 
manner  is  the  valued  dyestnff  known  as  indigo.  The  amount  of 
pure  colouring-matter  (indigotin)  contained  in  indigo  varies, 
being  generally  between  20  and  90  per  cent.  Besides  this,  it  con- 
tains various  substances :  indigo  red,  indigo  brown,  indigo  yellow, 
and  indiglutin,  of  most  of  which  but  little  is  known. 

Indigotin  occurs  sometimes  in  urine. 

Indigotin  is  best  obtained  from  indigo  by  conversion  of  the 
latter  into  the  soluble  reduced  compound,  and  subsequent  oxida- 
tion by  air  [30]  (indigo  vat) .  Another  method  consists  in  ex- 
tracting the  indigo  with  aniline  or  chloroform  and  allowing  the 
indigotin  to  crystallise  from  the  solvent.  According  to  the 
method  of  preparation,  indigotin  forms  lustrous  coppery  needles 
or  a  dark  blue  powder.  On  heating  it  does  not  melt,  but  sublimes 
with  partial  decomposition  in  form  of  coppery  needles.  Indigo 
vapour  has  a  purple-red  colour. 

Indigotin  is  insoluble  in  most  of  the  usual  solvents.  It  dis- 
solves in  aniline,  chloroform,  nitrobenzene,  phenol,  paraffin, 
petroleum,  naphthalene,  and  in  certain  fatty  oils.  The  solutions 
have  not  all  the  same  colour ;  for  example,  the  aniline  and  chloro- 
form solutions  have  a  deep  indigo-blue  colour,  while  the  solution 
in  paraffin  has  the  purple-red  colour  of  indigo  vapour,  a  behaviour 
somewhat  similar  to  that  of  iodine. 

The  composition  of  indigotin  corresponds  to  the  formula 
C8H5NO,  but  from  determination  of  its  vapour-density,  the 
molecule  contains  twice  this  and  is  therefore  C16H10N2O2. 

Indigotin  dissolves  unchanged  in  concentrated  sulphuric  acid 

Q 


226  CHEMISTRY  OF  ORGANIC  DYESTCJFFS. 

with  a  green  colour.  On  heating,  sulphonic  acids  are  formed,  the 
colour  of  the  solution  changing  to  blue. 

By  destructive  distillation,  indigotin  yields  aniline  ;  on  melting 
with  caustic  potash,  aniline,  anthranilic  acid,  and  salicylic  acid  are 
formed  [16]. 

Oxidising  agents  convert  indigotin  to  isatin  [16].  Chlorine 
produces  chlorine  derivatives  of  isatin  first,  and  then  chlorinated 
phenols  and  chloranil  [16] .  Bromine  acts  in  a  similar  manner. 

Indigotin  dissolves  in  hot  concentrated  caustic  potash  solution 
with  an  orange-yellow  colour,  indigo  white  and  isatic  acid  being 
probably  formed. 

On  reduction  in  alkaline  solution  indigo  blue  takes  up  two 
atoms  of  hydrogen,  forming  indigo  white,  which  possesses  phe- 
noloid  properties  and  dissolves  in  the  alkaline  liquid. 

In  the  air,  indigo  white  solution  oxidises  immediately,  insoluble 
indigo  blue  separating.  This  property  is  extensively  employed  in 
dyeing  with  indigo,  and  also  serves  for  the  isolation  of  pure  indigo 
from  the  commercial  product. 

The  reducing-agents  more  commonly  employed  are  ferrous  salts, 
arsenious  acid,  stannous  oxide,  hyposulphurous  acid,  zinc  powder, 
and  grape-sugar. 


Dilenzoylindigo  [32], 
C16H8N202(C7H50)2, 

is  formed  on  heating  indigotin  with  benzoyl  chloride. 

Halogen  derivatives  [33]  of  indigotin  have  been  prepared  from 
the  corresponding  derivatives  of  isatin  and  of  orthonitrobenz- 
aldehyde  [37]. 

Dinitro-  and  diamido-indigotin  have  been  prepared  from 
dinitro-isatin  [33]  .  (Compare  the  "  Synthesis  of  Indigo  Blue," 
p.  231.), 

Indigo    White, 


is  formed  by  reduction  of  indigotin,  and  contains  two  atoms  of 
hydrogen  more  than  the  latter.  In  distinction  from  indigotin, 
which  possesses  neither  basic  nor  acid  properties,  it  exhibits  the 


INDIGO  DYESTUFFS.  227 

character  of  a  weak  acid  like  the  phenols.  It  dissolves  in  alkalies, 
and  may  be  precipitated  from  the  solutions  by  an  acid.  Carbonic 
acid  separates  it  as  a  silky  greyish- white  mass.  Indigo  white  can 
only  be  dried  and  preserved  in  an  atmosphere  of  carbonic  acid  or 
hydrogen.  It  oxidises  rapidly  to  indigotin  on  exposure  to  the 
air.  From  the  properties  of  indigo  white,  it  is  apparent  that  the 
carbonyl  oxygen  atoms  of  the  indigotin  are  converted  into 
hydroxyl  groups. 

From  the   derivatives  of  indigo  blue    (sulphonic   acids,  &c.), 
substitution-derivatives  of  indigo  white  are  obtained  on  reduction. 


Indigo  Slue  Sulphonic  Acids. 

MonosulpJionic  Acid  [34], 

C16H9N202S03H, 
(Sulphopurpuric  Acid.} 

This  acid  is  obtained  by  heating  indigo  with  concentrated  sul- 
phuric acid.  It  forms  purple-red  flocks  which  dissolve  in  pure 
water  with  a  blue  colour,  but  are  insoluble  in  dilute  sulphuric 
acid.  The  salts  are  sparingly  soluble  in  water,  insoluble  in  saline 
solutions. 


Disulphonic  Acid  [34], 
C16H8N202(S03H)2, 

is  formed  by  further  action  of  sulphuric  acid  on  indigotin.  It 
forms  an  amorphous  powder,  soluble  in  water.  The  salts  are  also 
easily  soluble,  and  may  be  separated  from  aqueous  solutions  by 
addition  of  salt.  The  sodium  salt  comes  into  commerce  as  a  paste, 
and  is  known  as  Indigo  Extract,  Indigo  carmine,  &c.  It  is 
applied  like  the  acid  dyestuffs,  and  has  a  somewhat  extensive 
application  in  wool-dyeing.  Indigo-disulphonic  acid  may  also  be 
obtained  synthetically,  the  method  will  be  found  under  Synthesis 
of  Indigotin. 


Q2 


228  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


APPLICATION  OF  INDIGO  IN  DYEING. 

The  tinctorial  properties  of  indigo  are  due  to  the  presence  of 
the  chromophorous  group  : 

CO—  C 


which  forms  a  closed  chain  with  the  benzene  ring.  As  it  contains 
no  salt-forming  groups  it  is  not  a  real  dyestuff,  and  owing  to  its 
insolubility  has  no  affinity  for  the  fibre.  This  may  be  produced  by 
introduction  of  sulpho-  groups,  and  the  indigo  then  assumes  the 
character  of  an  acid  dyestuff.  The  principal  application  of  indigo 
depends,  however,  on  its  conversion  into  soluble  indigo.  The 
process  based  on  this  property  is  termed  vat-dyeing,  and  has  been 
in  use  since  the  earliest  periods.  Most  of  the  reducing-agents 
acting  in  alkaline  solution  have  been  applied,  but  in  practice  the 
following  are  important  :  —  Ferrous  sulphate,  stannous  chloride, 
grape-sugar,  arsenious  acid,  zinc  powder,  and  sodium  hydro- 
sulphite. 

The  reducing-  agent  employed  is  generally  added  along  with 
lime  or  soda  to  a  finely  divided  indigo  suspended  in  water.  The 
ferrous  sulphate  and  stannous  chloride  are  hereby  converted  to 
the  corresponding  hydrates.  The  indigo  blue  is  slowly  converted 
to  indigo  white,  which  dissolves  in  the  alkaline  liquid.  The  indigo- 
vat  is  used  for  dyeing  both  wool  and  cotton. 

Wool  appears  to  have  a  certain  attraction  for  indigo  white  and 
is  capable  of  withdrawing  it  from  solution,  while  cotton  is  only 
impregnated  with  the  liquid.  In  all  cases  the  conversion  of 
indigo  white  to  indigo  blue  on  the  fibre  is  effected  by  atmospheric 
oxidation.  Only  in  recent  years  has  indigo  been  applicable  for 
direct  printing.  Previously  calico  was  dyed  in  an  indigo-vat,  and 
then  the  necessary  effects  produced  by  printing  on  discharges. 
Of  late  years,  however,  the  following  methods  have  been  employed 
on  direct  printing. 

Cotton  fabrics  impregnated  with  grape-sugar  solutions  are 
printed  with  a  mixture  of  finely  divided  indigo  and  strong  caustic 
soda  suitably  thickened.  On  steaming  the  indigo  white  produced 


INDIGO  DYESTUFFS.  229 

thoroughly  penetrates  the  fibre,  and  on  oxidation  fast  indigo 
effects  are  obtained. 

The  difficulties  in  this  direction  have  also  been  to  a  certain 
extent  vanquished  by  the  introduction  of  artificial  indigo.  A 
thickened  mixture  of  orthonitrophenylpropiolic  acid  and  grape- 
sugar,  or  better  an  alkaline  xanthate  with  an  alkali  is  printed, 
and  the  indigo  blue  developed  by  steaming  and  drying. 

However,  orthonitrophenylpropiolic  acid  does  not  appear  to  have 
made  serious  competition  with  natural  indigo  in  this  direction, 
and  interesting  as  the  synthesis  is  from  a  scientific  standpoint,  it 
has  not  yet  been  applied  practically  to  any  great  extent. 

Indigo  carmine  is  almost  exclusively  used  in  wool-dyeing,  and  is 
applied  in  an  alum  bath  at  the  boil. 

The  shades  obtained  are  finer  than  those  from  the  vat,  but  are 
not  so  fast.  They  are  principally  used  in  production  of  mixed 
shades. 

Indigodicarbonic  Acid  [36], 
C16H8N202(COOH)2. 

This  acid  is  formed  by  treating  nitroterephthalaldehydic  acid, 

COOH     1 


NO,         2 

with  acetone  and  soda  solution,  and  by  action  of  alkali  and  grape- 
sugar  on  the  carbonic  acid  of  orthonitrophenylpropiolic  acid.  It 
forms  a  blue  precipitate,  insoluble  in  chloroform.  The  solution 
with  alkalies  is  green,  and  is  precipitated  by  acids. 

Indo'ine  [13], 

Indo'ine  is  formed  by  reduction  of  orthonitrophenylpropiolic 
acid  with  ferrous  sulphate  in  sulphuric  acid  solution.  It  closely 
resembles  indigo,  but  may  be  distinguished  by  the  following 
reactions  : — It  dissolves  in  cold  concentrated  sulphuric  acid  with  a 
blue  colour  (indigo  gives  a  green  solution),  and  is  only  converted 
into  a  sulphonic  acid  with  difficulty.  It  is  also  easily  soluble  in 
aniline  and  in  aqueous  sulphurous  acid,  forming  blue  solutions. 


230  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Indigopurpurin. 

C16H10N2O2. 

This  compound  is  isomeric  with  indigotin,  and  is  formed  as  a 
bye-product  in  the  preparation  of  the  latter  from  isatin  chloride 
[22,38]. 

It  is  similar  to  indigotin,  but  is  more  readily  sublimed,  forming 
fine  red  needles.  It  dissolves  in  alcohol  with  a  red  colour.  On 
dissolving  in  concentrated  sulphuric  acid  and  diluting  with  water, 
it  gives  a  red  solution. 


Indirulin  [13,  60]. 
C6H4—  CO—  C=C—  C  (OH)  =N. 

NH  ^C6H4 

Indirubin  is  the  indogenide  of  isatin,  and  is  isomeric  with 
indigotin.  It  may  be  obtained  by  mixing  aqueous  solutions  of 
indoxyl  and  isatin  in  presence  of  a  little  caustic  soda. 

Indirubin  forms  a  reddish-brown  powder.  It  dissolves  in 
alcohol  with  a  violet  colour,  and  in  concentrated  sulphuric  acid 
with  a  greyish-black  colour.  The  latter  solution  becomes  violet 
on  heating,  a  sulphonic  acid  being  formed.  With  reducing-agents 

gives  a  vat,  and  on  further  reduction  indileucin,  C16H12N2O,  is 
produced. 

From  the  present  state  of  our  knowledge,  it  is  not  certain  if 
mdigopurpurin  and  indirubin  are  identical  or  different. 


Indigo  Red  [61]. 

This  compound,  which  occurs  in  crude  indigo,  is  also  an  isomer 
of  indigotin.  The  exact  relationship  existing  between  this  body 
and  the  two  previous  ones  is  not  certain.  According  to  Baeyer,  it 
differs  from  mdigopurpurin. 

Schunck  obtained  a  compound  from  indican  which  he  named 
Indirubin,  and  which  he  regards  as  identical  with  indigo  - 
purpurin  [61]. 


INDIGO  DYESTUFFS.  231 

Indigo  red  forms  a  vat  and  a  sulphonic  acid,  both  capable  of 
dyeing.  The  shades  produced  in  the  vat  are  noteworthy  for  their 
extreme  fastness  to  light. 


SYNTHESIS  OF  INDIGO  BLUE. 

In  the  years  1865  and  1866  Baeyer  and  Knop  [14]  converted 
indigotin  through  dioxindol  and  oxindol  into  indol ;  and 
three  years  later  Baeyer  and  Emmerling  [5]  prepared  indol 
synthetically  by  melting- a  mixture  of  nitrocinnamic  acid,  caustic 
potash,  and  iron  filings.  The  nitrocinnamic  acid  employed  was  a 
mixture  of  the  ortho  and  para  compounds,  and  only  later  was  it 
discovered  that  the  ortho  acid  is  alone  capable  of  yielding  indol. 
In  1870  the  same  chemists  observed  the  formation  of  indigo 
blue  by  treating  isatin  with  a  mixture  of  phosphorus  trichloride 
and  acetyl  chloride. 

In  the  same  year  Emmerling  and  Engler  [39]  obtained  small 
quantities  of  indigo  by  heating  nitroacetophenone  with  zinc 
powder  and  soda-lime,  but  subsequently  were  unsuccessful  in 
producing  the  necessary  conditions  for  the  formation  of  the 
dyestuffs. 

The  first  certain  method  for  producing  artificial  indigo  is  due  to 
Nencki,  who  obtained  it  by  oxidation  of  indol  with  ozone  [40] . 
The  same  chemist  had  already  obtained  indol  by  the  pancreatic 
fermentation  of  albumen  [2,  40].  In  1877  Baeyer  and  Caro 
obtained  indol  by  passing  the  vapour  of  certain  aromatic  amines, 
especially  of  diethylorthotoluidine,  through  a  red-hot  tube. 

In  1878  the  constitution  of  oxindol  was  discovered  by  Baeyer 
[17]  and  by  Suida  [15].  It  was  found  to  be  the  inner  anhydride 
of  orthoamidophenylacetic  acid,  and  was  obtained  synthetically 
from  the  latter. 

In  the  same  year  [17]  Baeyer  prepared  isatin  from  oxindol. 
The  nitroso-compound  of  oxindol  yields  the  amido-compound  on 
reduction,  and  this  is  converted  into  isatin  by  oxidation  or  by 
nitrous  acid. 

As  isatin  had  already  been  converted  into  indigo,  the  forma- 
tion of  the  former  from  orthoamidophenylacetic  acid  effects  a 
complete  synthesis  of  indigo.  At  the  same  time  Baeyer  [17] 
improved  the  process  whereby  isatin  was  converted  into  indigo. 


232  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Isatin  is  first  submitted  to  the  action  of  phosphorus  tri-  or  penta- 
chloride,  and  the  resulting  isatin  chloride  yields  indigotin  on 
reduction.  In  this  case  indigopurpurin  is  formed  as  a  bye- 
product. 

Claisen  and  Shadwell  discovered  a  new  synthetical  method  for 
production  of  isatin  in  1879.  By  action  of  silver  cyanide  on 
orthonitrobenzoyl  chloride,  orthonitrobenzoyl  cyanide  is  produced, 
and  this  is  converted  into  orthonitrophenylglyoxylic  acid  by 
saponification  and  subsequent  treatment  with  an  alkali.  On 
reduction  of  this  acid  in  alkaline  solution,  a  salt  of  isatic  acid 
(orthoamidophenylglyoxylic  acid)  is  produced,  from  which  isatin 
may  be  separated  by  an  acid. 

These  researches  effect  another  complete  synthesis  of  indigotin. 

In  1880  Baeyer  prepared  indigo  synthetically  from  cinnamic 
acid  by  various  processes  [19,  41]  :  — 

I.  Orthonitrocinnamic  acid, 


=  CH—  COOH     [1] 
C6H4 

N02  [2] 

unites  with  bromine  to  form  orthonitrodibromhydrocinnamic  acid, 

CHBr-CHBr-COOH     II] 
C6H4< 

N02  [2] 

On  treating  this  compound  with  alkalies,  two  molecules  of 
HBr  split  off  and  an  unsaturated  acid  —  orthonitrophenylpropiolic 
acid, 

C=C-COOH     [1] 

N02  [2] 

is  formed.  This  acid  yields  isatin  on  boiling  with  an  alkali,  and 
indigo  on  reduction  in  an  alkaline  solution  (alkaline  grape-sugar 
solution,  or  an  alkaline  xanthate)  . 

II.  By  treating  Orthonitrocinnamic  acid  with  chlorine  in 
alkaline  solution,  orthonitrophenylchlorlactic  acid  is  formed 
according  to  the  equation  :  — 


INDIGO  DYESTUFFS.  233 

CHOH-CHC1 

CH  =  CH-COOH  /  | 

C6H/  +HC10  =  C6H4x  COOH. 

N02  \ 

N02 

This  acid  gives  orthonitrophenyloxyacrylic  acid  on  treating  with 
an  alkali, 

O 


CH-CHCOOH 
C6H4< 

NO2 

On  heating  in  phenol,  or  glacial  acetic-acid  solution,  this  com- 
pound yields  indigo. 

III.  Orthonitrophenylpropiolic   acid    yields   orthonitrophenyl- 
acetylene  on  boiling  with  water  [42]  : 

C^CH 
C6H4< 

N02 

On  oxidation  of  the  copper  compound  of  the  latter  with  potas- 
sium ferricyanide,  dinitrodiphenyldiacetylene  is  produced  : 

C=C— C=C 

C^H^x  /C6H4. 

NO2        NO2 

On  treatment  with  fuming  sulphuric  acid  this  body  undergoes 
a  molecular  change,  an  isomer,  diisatogen,  being  formed.  The 
latter  gives  indigo  on  reduction  [42] . 

IV.  In  1882  orthonitrobenzaldehyde  was  used  as  a  starting- 
point  for  the  artificial  production  of  indigotin  [2]. 

On  dissolving  orthonitrobenzaldehyde  in  acetone  and  adding 
an  excess  of  dilute  caustic-soda  solution,  indigo  blue  separates  on 
standing.  The  acetone  may  be  replaced  by  acetaldehyde  or 
pyruvic  acid.  This  reaction  was  studied  in  detail  by  Baeyer  [44], 
The  interaction  of  acetone  and  orthonitrobenzaldehyde  results  in 
the  formation  of  an  intermediate  product  of  the  composition 
C10HnNO4  (probably  the  methyl  ketone  of  orthonitrophenyl-1 


234  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

acid).     This  compound  decomposes  under  the  influence  of  alkalies 
according  to  the  equation  : 

2C10HnN04  +  2H20  =  C16H10N202  +  2C2H4O2  +  4H2O, 

indigotin  and  acetic  acid  being  formed. 

With  acetaldehyde,  orthpnitrobenzaldehyde  forms  the  aldehyde 
of  orthonitrophenyl-lactic  acid  : 

CHOH-CH.COH, 


which  splits  up  with  alkalies,  forming  indigotin  and  formic  acid 
[45]  .  The  intermediate  product  in  the  case  of  pyruvic  acid  is 
orthonitrocinnamyl-formic  acid  [44]  : 

CH=  CH—  CO—  COOH. 


This  body  is  best  obtained  by  action  of  ga'seous  hydrochloric 
acid  on  a  mixture  of  the  reacting  compounds.  Orthonitrocinnamyl- 
formic  acid  is  split  up  by  alkalies  into  indigotin  and  oxalic  acid. 

A  patent  of  Meister,  Lucius,  &  Briining  [46]  depends  on  a 
similar  reaction.  Claisen's  benzylidene-acetone  (cinnamylmethyl- 
ketone  C6H5—  CH  =  CHCO—  CH3)  [47]  ,  obtained  by  condensation 
of  benzaldehyde  and  acetone,  is  nitrated.  A  mixture  of  ortho  and 
paranitro  derivatives  is  formed,  and  the  former  yields  indigotin 
by  action  of  alkalies. 

Ortho-nitrometa-tolualdehyde  [48]  gives  a  homologue  of  indigo- 
blue,  and  chlorine  derivatives  may  be  obtained  from  chlor-ortho- 
nitroaldehydes  [37]  .  Another  method  has  its  starting-point  in 
ortho-amidoacetophenone.  This  compound  is  converted  into  its 
acetyl  derivative  and  treated  with  bromine  in  the  cold.  The  re- 
sulting bromine  derivative,  when  dissolved  in  concentrated  sul- 
phuric acid,  loses  hydrobromic  acid,  a  crystalline  compound  being 
formed,  which,  under  the  influence  of  air  in  presence  of  alkalies, 
yields  indigotin. 

Indigotin  may  also  be  obtained  from  ortho-amidophenylacety- 
lene  by  an  analogous  process. 

Gevekoht  [50]  obtained  indigotin  by  action  of  ammonium  sul- 
phide on  ortho-nitroacetophenone,  in  which  the  methyl  group  is 
brominated. 


INDIGO  DYESTUFFS.  235 

From  the  researches  of  Baeyer  [51]  and  Bloem  it  is  shown  that 
on  brominating  acetylortho-amidoacetophenone,  the  bromine  atom 
enters  in  the  methyl  group.  If  the  benzene  chain  is  substituted 
brominated  indigos  are  formed ;  but  if  only  the  benzene  chain  con- 
tains bromine^  indigo  cannot  be  produced.  Tn  these  reactions 
indoxyl  appears  to  be  formed  as  an  intermediate  product  in  the 
reaction. 

P.  Meyer  [52]  prepared  substituted  indigo  blues  from  the 
corresponding  substituted  isatins.  This  process  depends  on  the 
fact  that  the  final  products  of  the  action  of  dichloracetic  acid  on 
amines  in  which  the  para  position  is  occupied  are  substituted 
isatins.  The  first  product  of  the  action  of  dichloracetic  acid  on 
paratoluidine  is  a  paratolylimide  derivative  of  paramethyli satin, 
C16H16N2O,  which  decomposes  on  boiling  with  acids  into  para- 
toluidine and  methylisatin,  C9H7NO2. 

Perhaps  the  simplest  methods  for  the  synthetic  production  of 
indigo  are  those  which  have  their  starting-point  in  certain  aniline 
derivatives  of  acetic  acid.  Flimm  discovered  that  bromacetanilide, 
C6H5NH — CO — CH2Br,  gives  a  trace  of  indigo  on  heating  with 
caustic  potash  (B.  B.  1890,  p.  57).  Heumann's  process  gives  a 
somewhat  better  result,  but  still  the  yield  (about  15  per  cent.)  is  not 
sufficiently  great  for  technical  application.  In  this  method  phenyl- 
glycocine,  formed  by  action  of  monochloracetic  acid  on  aniline,  is 
heated  with  caustic  potash  with  exclusion  of  air  to  about  260°. 
The  orange-yellow  melt  obtained  is  dissolved  in  water,  and  on  ex- 
posure to  air  indigo  separates.  The  course  of  the  reaction  is  not 
exactly  understood,  but  in  all  probability  the  first  stage  consists  in 
the  formation  of  pseudoindoxyl : 


IH 

C6H4  .  NH  .  CH2CO|OH 


In  alkaline  solution  pseudoindoxyl  oxidises  immediately,  pro- 
ducing indigo  : 


C  O  C  ( 


236 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


A  somewhat  better  result  is  obtained  by  using  phenylglycocine- 
orthocarbonic  acid,  which  is  prepared  by  action  of  monochloracetic 
acid  on  anthranilic  acid.  This  compound  is  fused  with  caustic 
potash,  the  reaction  taking  place  at  a  considerably  lower  tempera- 
ture than  when  phenylglycocine  is  employed. 

If  phenylglycocine  is  mixed  with  sand  and  introduced  into  a 
large  quantity  of  sulphuric  acid  containing  a  considerable  amount 
of  sulphuric  anhydride,  taking  care  to  avoid  an  increase  in  tem- 
perature, a  reaction  immediately  takes  place,  sulphurous  acid  being 
evolved,  while  the  solution  takes  a  blue  colour.  This  is  due  to 
the  formation  of  indigo-disulphonic  acid,  which  may  easily  be 
isolated  by  dilution  and  addition  of  salt.  The  yield  by  this  pro- 
cess is  satisfactory,  amounting  to  about  60  per  cent,  of  the  phenyl- 
glycocine used. 


CONSTITUTION  OF  THE  INDIGO  GROUP. 

From    his    synthesis    of  indol   from   orthonitrocinnamic   acid 
Baeyer  ascribed  to  it  the  constitutional  formula  : 

/CH\ 
H4C6  CH, 


which  is  now  generally  accepted. 

Kekule  had  already  (1869)  [53]  published  an  opinion  that 
isatin  is  an  inner  anhydride  of  orthoamidophenylglyoxylic  acid, 
and  accordingly  suggested  the  structural  formula  : 

/CO 

C6H4<(       ">CO. 
NET 

Claisen  and  Shadwell  proved  that  isatic  acid  is  orthoamido- 
phenylglyoxylic acid,  and  that  isatin  is  its  inner  anhydride  by  a 
direct  synthesis  [26].  However,  various  properties  of  isatin 
noted  by  Baeyer  speak  for  the  presence  of  an  hydroxyl  group 
according  to  the  formula  : 


INDIGO  DYESTUFFS. 


237 


Oxindol  is,  from  its  synthetic  production,  an  inner  anhydride 
of  orthoamidophenylacetic  acid,  and  has  the  formula  : 


:CO. 


The  formation  of  oxindol  and  dioxindol  by  reduction  of  isatin 
is,  however,  more  in  favour  of  the  following  constitution  for  these 
compounds : — 

f^  TJ  ( (~\  U  \  C*f\  TJ  r^ZT          r^l(~\~LX\ 

/\JITL  (UrlJL'Uxl  ,  Ujl2 — U(Url) 

CTT    /  .^  tl    TJ    / 

6"4\  ^6^-4^  ^^ 

^-N^  ^N^ 

Dioxindol.  Oxindol. 

The  constitution  of  indoxyl  may  be  deduced  by  its  formation 
from  indoxylic  acid  : 

r\(C\\3\      r\      r\c\  TJ 
i'\~>  \  \Jr\-)  =v>--^— L/L/gJcl 

C6H4^ 

^NH^ 

The  hydroxyl  group  must  be  in  combination  with  the  carbon 
atom  in  the  adjacent  position  to  the  benzene  ring.  The  constitu- 
tion of  indoxyl  is  accordingly  represented  by  the  formula 


C6H4 


XC(OH)— CH 


NH 


From  certain  reactions  it  appears  probable  that  isatin,  indoxylic 
acid,  and  indoxyl  are  capable  of  existing  in  two  isomeric  forms. 
One  of  these  exists  only  in  the  form  of  derivatives  (for  example, 
ethers) .  Baeyer  terms  these  ' '  labile  or  pseudo  forms/''  and  gives 
the  following  formulas  to  them  : — 


.CO-COH 


cfia 


Isatin. 
C6H4C(OH)=CH 


/CO— CO 

C6H4^       / 

Tseudoisatin. 
C6H4— CO— CH2 


Indoxyl, 


Pseudoindoxyl. 


238  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

C6H4—  C  (OH)  ^C—  COOH        C6H4—  CO—  CH—  COOH 


Indoxylic  acid.  Pseudoindoxylic  acid. 

These  pseudo-modifications  are  stable  when  certain  of  their 
hydrogen  atoms  are  replaced.  In  the  case  of  pseudoisatin  a 
monovalent  group  suffices  ;  while  in  pseudoindoxyl  both  hydrogen 
atoms  of  the  carbon  atom  in  the  side-ring  must  be  replaced.  In 
this  manner  the  following  compounds  may  be  obtained  :  — 

C6H4—  CO—  CO  C6H4—  CO—  C=CHC6H5 


NC2H5 

Ethylpseudoisatin.  Benzylidenepseudoindoxyl. 

The  divalent  rest  of  pseudoindoxyl, 

C6H4—CO—  C= 

w 

is  especially  interesting,  as  researches  on  this  subject  show  that  it 
must  be  contained  in  indigotin.  Baeyer  designates  this  rest  as 
the  indogene  group,  and  those  derivatives  in  which  the  indogene 
group  replaces  an  atom  of  oxygen  are  termed  indogenides.  The 
above  benzylidenepseudoindoxyl  must  therefore  be  regarded  as 
the  indogenide  of  benzaldehyde,  as  it  is  formed  by  heating  indo- 
xylic  acid  with  benzaldehyde,  carbonic  acid  and  water  splitting  off. 
Indigotin  may  be  regarded  as  a  combination  of  two  indogene 
groups,  as  expressed  by  the  constitutional  formula  : 

C6H4—  CO—  C  =C—  CO—  C6H4 


Indigotin. 

This  constitution  is  also  that  of  an  indogenide  of  pseudoisatiu  : 

.CO—  CO 

c6H4<; 

XNH 
and  indigotin  is  therefore  formed  by  replacement  of  an  oxygen 


INDIGO  DYESTUFFS.  239 

atom  of  pseudoisatin  by  the  indogene   group.      Similarly,  indi-- 
rubin  is  the  indogenide  of  isatin  : 

C6H4—  CO—  C=C—  C(OH)=:N 


Indirubin  is  formed  by  action  of  isatin  on  iudoxyl,  in  which 
reaction  it  must  be  accepted  that  the  latter  undergoes  a  molecular 
change  into  pseudoindoxyl. 

Baeyer  arrives  at  these  conclusions  from  the  following  facts  :  — 
By  the  action  of  nitrous  acid  on  indoxyl  a  nitrosamine  of  the 
latter  is  formed  : 

CTT 
-" 

N(NO) 

On  reduction  it  is  converted  through  indoxyl  to  indigotin. 
By  action  of  nitrous  acid  on  ethylindoxylic  acid  [56]  an  isomeric 
compound,  possessing  the  properties  of  an  isonitroso  compound,  is 
formed.  It  yields  isatin  on  reduction  and  subsequent  oxidation. 

It  is  probable  that  in  the  formation  of  this  body  from  ethyl- 
indoxylic acid  : 


a  molecular  change  takes  place,  as  two  monovalent  groups  are 
split  off  from  two  different  carbon  atoms,  and  the  isonitroso  group 
is  always  divalent  and  connected  with  one  carbon  atom. 

The  formation  of  isatin  from  this  body  shows  it  to  be  pseud- 
isatoxime  or  isonitrosopseudoindoxyl  : 

CO—  C=NOH. 


This  constitution  receives  further  support  from  the  behaviour 
on  ethylation,  whereby  a  mono-ethyl  ether  is  produced.  This  ether 
also  yields  isatin,  and  therefore  cannot  contain  the  ethyl  group 
in  direct  combination  with  a  carbon  atom,  nor  yet  in  the  imide 
group.  It  is  stable  to  hydrochloric  acid,  which  would  not  be  the 
case  were  the  ethyl  group  connected  with  hydroxyl. 


240  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

.    The  constitution  of  the  compound  is  therefore  expressed  by  the 
formula  : 

XCO—  C=NO(C2H5) 
C6H4\    ^ 
XNH 

It  is  pseudoisatinethyl-a-oxime.       On   further  ethylation  the 
di  ethyl  ether  is  formed  : 

CO—  C=NOC2H5 


On  reduction   and  subsequent  oxidation,   ethylpseudoisatin    is 

formed  : 

CO—  CO 


It  differs  from  the   isomeric  ethylisatin  by   being  difficult  to 
saponify.     Alkalies  convert  it  to  ethylisatic  acid  : 

CO—  COOH 
C6H4<T 

XNHC2H5 

With  hydroxylamine  ethylpseudoisatin  gives  the  /3-oxime 

,C(NOH)—  CO 


It  combines  with  indoxyl  to  form  the  indogenide 
C6H4—  CO—  C=C—  CO—  NC2H6 


The  diethyl  ether  of  pseudoisatin-a-oxime  yields  diethyl 
indigo  blue  if  treated  with  mild  reducing-agents,  precisely  in  the 
same  manner  that  pseudoisatoxime  gives  indigo  blue  under  similar 
conditions. 

As  in  this  reaction  the  ethylated  isonitroso  group  is  split  off, 
while  the  ethyl  group  attached  to  the  imide-nitrogen  atom  remains 
intact,  it  follows  that  if  the  above  constitution  of  ethyl  pseudo- 


INDIGO  DYESTUFFS.  241 

isatin   ethyl  a-oxime  is    correct,    diethyl-indigotin  must  possess 
the  constitution  expressed  by  the  formula  : 

C6H4— CO— C=C_ CO— C6H4 ; 


C2H5  NC2H5 

and  consequently  indigotin  the  analogous  one  : 
C6H4—  CO—  C=C—  CO—  C6H4. 


Baeyer  summarises  the  conclusions  leading  to  this  formula  as 
follows  :  —  \ 

1.  Indigotin  contains  an  imi  do-group. 

2.  Its  formation    from   diphenyl-diacetylene    shows    that    the 
carbon  atoms  are  placed  in  the  following  manner  :  — 

C6H5  —  C  —  C  —  C  —  C  —  C6H5. 

3.  Indigotin  is  formed  only  from  those  compounds  in  which  the 
carbon  atom  adjacent  to  the  benzene  ring  is  connected  with  an 
atom  of  oxygen. 

4.  The    formation  and  properties  of  indigotin  show  a  close 
relationship  to  indirubin  and   to  the  indogenide  of  ethylpseudo- 
isatin.      The  latter  is   formed  by  the  coupling  of  the  a-carbon 
atom  of  pseudoindoxyl  with  the  /3-carbon  atom  of  pseudoisatin. 


242  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


CHAPTER  XII. 
EUXANTHIC  ACID  AND  GALLOFLAYINE. 

THESE  yellow  dyestuffs,  though  of  totally  different  origin,  show 
some  relationship  in  chemical  properties,  and  possibly  owe  their 
tinctorial  value  to  the  same  chromophor.  In  euxanthic  acid  this 
is  a  carbonyl  group,  which  forms  a  ring  with  one  oxygen  atom  and 
two  benzene  nuclei. 

Euxanthic  acid  contains  as  chromogen  the  rest  of  diphenylene- 
ketone-oxide : 


somewhat  similar  in  constitution  to  anthraquinone, 

CO/C6H4\CO 

XC6H/ 

It  has  not  been  determined  with  certainty  that  galloflavine 
contains  the  same  group. 

Euxanthic  Acid. 

CieHisOn. 

The  magnesium  salt  is  the  essential  constituent  of  the  dyestuff 
known  in  commerce  as  Purree  or  Indian  Yellow.  This  product  is 
obtained  from  the  urine  of  cows,  fed  on  mango-leaves.  The  gold- 
yellow  urine  is  heated,  and  the  yellow  deposit  formed  into  a  ball. 
This  is  purified  by  removing  the  outer  portions  and  thoroughly 
washing  the  remainder. 

The  recent  researches  of  v.  Kostanecki  [8]  demonstrate  that  the 
origin  is  from  urine,  as  they  proved  that  the  urine  of  animals  whose 
food  contained  euxanthone  separated  euxanthic  acid.  It  is  probable 


EUXANTHIC  ACID  AND  GALLOFLAVINE.  243 

that  the  euxanthone  contained  in  certain  plants  combines  with 
glucuronic  acid  in  the  animal  organism,  euxanthic  acid  thus  being 
formed.  To  prepare  euxanthic  acid,  purree  is  exhausted  with  water, 
treated  with  dilute  hydrochloric  acid,  and  the  residue  extracted 
with  ammonium  carbonate.  The  resulting  ammonium  salt  is  de- 
composed with  hydrochloric  acid,  and  the  euxanthic  acid  crystallised 
from  alcohol  (2). 

It  forms  lustrous  straw-yellow  needles,  sparingly  soluble  in  cold 
water,  more  easily  in  hot  water,  and  readily  in  alcohol,  but  in- 
soluble in  ether. 

On  heating  to  130°  one  molecule  of  water  splits  off,  an  anhydride, 
C19H16O10  [6],  being  formed.  This  was  formerly  regarded  as 
anhydrous  euxanthic  acid,  the  crystallised  acid  having  the  formula 
C]9H16O10  +  H20.  Euxanthic  acid  is  monobasic;  its  salts  with  the 
alkalies  are  easily  soluble,  those  with  magnesium  and  lead  sparingly 
soluble.  The  alkali  salts  are  precipitated  by  an  excess  of  alkali. 
On  heating  with  water  or  dilute  sulphuric  acid  to  140°,  euxanthic 
acid  splits  up  into  euxanthone  [1],  C13H8O4,  and  glucuronic  acid, 
C6H1007  [6]. 

Euxanthone  is  also  formed  by  heating  euxanthic  acid  to  160— 180°, 
or  by  warming  with  concentrated  sulphuric  acid  |  38] . 

Chlorine  and  bromine  act  on  euxanthic  acid,  producing  di-sub- 
stitution  products  [2] .  Nitric  acid  produces  nitro-euxanthic  acid 
in  the  cold  ;  on  warming,  trinitro-euxanthone,  and  finally  styphnic 
acid  is  formed  [1]. 

Euxanthone. 
C13H804. 

This  compound  forms  pale  yellow  needles  which  sublime  without 
decomposition.  It  is  insoluble  in  water,  sparingly  soluble  in  ether, 
easily  in  boiling  alcohol.  It  is  formed  as  described  above  from 
euxanthic  acid,  and  is  also  a  constituent  of  purree,  the  lower 
qualities  containing  most.  It  is  soluble  in  aqueous  solutions 
of  the  alkalies,  but  possesses  no  further  acid  properties.  Its 
alcoholic  solution  is  precipitated  by  lead  acetate.  On  heating  with 
zinc  powder,  benzene,  phenol,  and  methylenediphenylene-oxide, 
CH2— (C6H4)2O  [9],  are  formed.  The  last-named  compound 
yields  diphenyleneketone- oxide  on  oxidation, 

O/C6H4\CO 
XC6H/ 

R2 


244 


CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


Diacetyleuxanthone  is  formed  ou  boiling  euxanthone  with  acetic 
anhydride,  M.P.  185°.  Dichloreuxanthone  and  dibromenxanthone 
maybe  produced  by  decomposition  of  the  corresponding  derivatives 
of  euxanthic  acid  [2] . 

Trinitroeuxantlione  forms  yellow  needles,  and  is  a  monobasic  acid 
[2]. 

The  constitution  of  euxanthone  is  explained  by  the  following  re- 
searches of  Baeyer  and  Graebe  [21]  .  On  melting  with  potash  it 
yields  euxanthonic  acid  (tetraoxybenzophenone), 


OH 


OH    OH 


-CO  — 


OH 


which  on  further  heating  splits  up  into  resorcin  and  hydroquinone. 
Euxanthone  is  the  inner  anhydride  of  euxanthonic  acid, 


—  0  — 


— co- 


and  is  therefore  2.6  dioxydiphenyleneketone-oxide.  This  is  con- 
firmed by  its  synthesis,  on  heating  hydroquinone  carbonic  acid  with 
/3-resorcylic  acid  in  presence  of  acetic  anhydride. 

Euxanthic  acid  is  apparently  an  ether  of  euxanthone  (or  euxan- 
thonic acid)  with  glucuronic  acid. 


C6H10O7  =  C19H18O 


Euxanthone. 


Glucuronic 
acid. 


Euxanthic 
acid. 


Euxanthone,  although  yellow,  is  not  a  dyestuff,  while  euxanthic 
acid  is  capable  of  dyeing  on  metallic  mordants. 

Its  principal  application  is  as  an  artists'  pigment  under  the  name 
of  Indian  Yellow. 


EUXANTHIC  ACID  AND  GALLOFLAVINE.  245 

SYNTHETICAL  OXYKETONE  DYESTUFFS  [22]. 

A  method  for  the  production  of  hydroxyl  derivatives  of  benzo- 
phenone  and  its  homologu.es  has  been  patented  by  the  Badische 
Anilin-  und  Sodafabrik. 

The  process  consists  in  heating  fatty  or  aromatic  acids  with 
a  phenol  or  oxycarbonic  acid  containing  at  least  two  hydroxyl 
groups  in  the  ortho  position  to  each  other  with  a  dehydrating  agent. 
The  reaction  may  be  best  explained  by  the  following  example. 

Trioxybenzophenone. 

One  part  of  pyrogallol  and  one  part  of  benzoic  acid  are  heated 
to  145°,  and  three  parts  of  zinc  chloride  gradually  stirred  into  the 
mixture,  and  the  above  temperature  maintained  for  three  hours. 
The  melt  is  extracted  with  boiling  water,  and  on  cooling  the  dye- 
stuff  is  deposited  in  yellow  needles,  M.P.  137-138°.  It  dyes 
golden-yellow  shades  on  cotton  mordanted  with  alumina  ;  the 
presence  of  lime-salts  renders  the  tone  more  orange.  Another 
process  for  production  of  trioxybenzophenone,  due  to  the  same 
firm,  consists  in  heating  pyrogallol  with  benzotrichloride  in 
aqueous,  alcoholic,  or  acetic  acid  solution.  It  is  known  in  com- 
merce as  Alizarin  Yellow  A. 

Gallacetoplienone. 

This  compound  is  a  trioxyacetophenone  {  (OH)3C6H2COCH3^ 
obtained  by  heating  pyrogallol  with  acetic  acid  and  zinc  chloride 
to  150°.  It  may  be  used  for  printing  with  chromium  acetate,  and 
gives  brown  shades  [23]  .  It  is  named  Alizarin  Yellow  Gr. 

Ellagic  Acid. 


This  compound  is  related  to  the  above  dyestuffs  and  to  gallo- 
flavine,  although  its  constitution  has  not  been  determined  with  cer- 
tainty. Ellagic  acid  may  be  obtained  by  action  of  various  oxidising 
agents  on  gallic  and  tannic  acids,  and  by  heating  gallic  ether  with 
soda  solution.  It  also  occurs  naturally  in  bezoar  stones.  Ellagic  acid 
gives  greenish-yellow  shades  when  printing  with  chromium  acetate. 


246  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Gallqflavine. 

This  dyestuff  is  formed  by  oxidation  of  a  gallic  acid  solution, 
containing  about  two  molecules  of  an  alkali,  by  atmospheric  oxygen 
[12].  It  is  best  prepared  by  dissolving  gallic  acid  in  alcoholic 
potash  solution,  and  passing  a  current  of  air  through  the  solution. 
A  potassium  salt  of  the  dyestuff,  which  is  sparingly  soluble  in 
alcohol,  separates  [11]. 

Galloflavine  forms  greenish-yellow  leaflets,  sparingly  soluble  in 
ether  and  alcohol,  more  easily  in  acetic  acid,  and  best  in  aniline.  It 
is  soluble  in  alkalies,  and  is  reprecipitated  on  the  addition  of  acids. 

The  composition  of  galloflaviue  is  probably  represented,  by  the 
formula  C13H6O9. 

It  forms  dibasic  salts ;  those  with  the  alkalies  are  easily  soluble 
in  water. 

If  heated  with  acetic  anhydride,  it  yields  a  colourless  acetyl 
compound,  C13H209(Ci!H3O)4/M.P.  230°  [11]. 

Galloflavine  is  used  along  with  metallic  mordants.  On  alumina 
it  produces  a  greenish-yellow  shade,  on  tin  oxide  a  pure  yellow, 
and  on  chromium  oxide  an  olive-green.  It  has  been  used  to 
a  slight  extent  in  wool-dyeing ;  on  chromed  wool  it  gives  results 
similar  to  fustic. 


CANARINE.  247 


CHAPTER  XIII. 

CANAEINE.    [13,  14,  15.] 

ON  treating  potassium  sulphocyanide  with  potassium  chlorate,  in 
presence  of  hydrochloric  acid,  canarine  is  formed  (Prokoroff  and 
Miller)  [13]. 

This  compound  is  probably  identical  with  that  discovered  by: 
Liebig  [16],  and  named  pseudo-  or  persulpho-cyanogen,  C3N3HS3, 
although  the  identity  of  the  two  is  denied  by  Miller. 

Canarine  forms  a  yellow  powder,  insoluble  in  neutral  solvents, 
soluble  in  alkalies  and  in  borax  solution. 

The  application  of  canarine  depends  on  its  property  of  dyeing 
cotton  yellow  from  an  alkaline  solution.  The  shades  vary  from 
light  yellow  to  orange-yellow,  according  to  the  concentration  of 
the  solution.  They  are  very  fast  both  to  soap  and  light.  In  com- 
parison with  other  artificial  dyestuffs,  canarine  only  possesses  weak 
tinctorial  properties. 

Canarine  dyed  on  cotton  is  capable  of  acting  as  a  mordant  for 
basic  dyestuffs.  In  this  respect  it  resembles  Cachou  de  Laval  and 
the  benzidine  series  of  direct  colours. 


248  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


CHAPTER  XIV. 

MUREXIDE.    [17,  18,  19,  20.] 

MUREXIDE  is  the  acid  ammonium  salt  of  purpuric  acid,  which  does 
not  exist  in  the  free  state.  It  is  of  historical  interest,  as  besides 
picric  acid  it  is  the  oldest  artificial  dyestuff  used  technically.  Its 
application  dates  from  the  year  1853. 

Murexide  is  obtained  by  action  of  ammonia  on  the  mixture 
of  alloxan  and  alloxantin,  obtained  by  evaporating  a  solution  of 
uric  acid  in  strong  nitric  acid. 

It  is  formed  further  by  heating  alloxantin  in  ammonia  gas,  and 
boiling  uramil  with  mercuric  oxide. 

It  forms  four-sided  prisms,  with  a  green  lustre,  appearing  red 
by  transmitted  light. 

The .  composition  of  murexide  is  expressed  by  the  formula 
C8H4N5O6NH4.  By  double  decomposition  with  potassium  nitrate, 
the  potassium  salt  (C8H4N6O6K)  is  obtained.  The  salts  with 
calcium,  barium,  tin,  and  mercury  are  sparingly  soluble  red  or 
violet  precipitates. 

Murexide  dissolves  in  water  with  a  fine  purple-red  colour,  which 
is  changed  to  blue-violet  on  addition  of  excess  of  alkali.  Mineral 
acids  set  free  purpuric  acid,  which  immediately  decomposes  into 
uramil  and  alloxan,  the  solution  being  decolorised. 

Murexide  may  be  dyed  on  tin,  lead,  or  mercury  mordants,  the 
last  producing  the  best  results.  It  is  at  present  out  of  use. 


DYESTUFFS  OF  UNKNOWN  CONSTITUTION.  249 


CHAPTER  XV. 

DYESTUFFS  OF  UNKNOWN  CONSTITUTION. 

THE  following  chapter  comprises  those  dyestuffs  which  cannot  be 
placed  under  the  foregoing  chemical  classifications.  It  has  already 
been  mentioned  that  many  of  the  dyestuffs  treated  of  under  the 
previous  groups  are  of  unknown  constitution ;  but,  being  products 
of  chemical  synthesis,  certain  relationships  to  the  various  classes 
are  easily  deduced. 

The  number  of  colouring-matters  included  in  the  present  chapter 
is  unfortunately  very  large ;  most  of  them  are  natural  products 
obtained  from  plant  and  animal  sources.  As  these  natural  dyestuffs 
are  very  numerous,  only  those  are  described  which  are  of  interest 
from  a  technical  or  scientific  point  of  view. 

Although  the  artificial  dyestuffs  have  to  a  great  extent  replaced 
the  natural  ones,  certain  of  the  latter  still  retain  great  importance 
in  dyeing,  being  in  fact  indispensable,  as  no  synthetical  products 
have  been  able  to  do  their  work. 

The  great  importance  of  a  large  number  of  the  natural  dyestuffs 
is  based  on  the  property  which  they  possess  of  forming  firmly- 
adherent  lakes  with  metallic  oxides.  They  are,  like  alizarin, 
adjective  dyestuffs. 

Some  of  them,  for  example  Hsematoxylin,  Hsemate'in,  Brasilin, 
and  Brasilei'n,  are  possibly  quinones ;  others  appear  to  be  related 
to  Euxanthone. 

Some  of  these  compounds  are  glucosides,  which  may  be  split  up 
by  action  of  dilute  acids,  forming  a  sugar,  and  a  compound  which 
is  the  real  colouring-matter. 

Some  natural  dyestuffs  (Curcumin,Bixin,Carthamin)  are  capable, 
like  the  tetrazo  dyestuffs,  of  dyeing  on  unmordanted  cotton. 


250  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Hcematoxylin  [1,  2,  3,  13]. 
Ci6HHO6. 

Haematoxylin  is  contained  in  logwood  or  campeachy,  the  wood 
of  Haematoxylon  campechianum.  Although  scarcely  a  dyestuff, 
hsematoxylin  is  the  only  important  constituent  of  logwood,  as  on 
oxidation  it  yields  haematem  [2] ,  a  compound  of  strong  tinctorial 
properties. 

Heematoxylin  is  prepared  by  extracting  freshly  rasped  logwood 
with  aqueous  ether,  evaporating,  and  mixing  the  residue  with 
water  [3] .  The  crystals  which  separate  are  recrystallised  from 
water,  preferably  with  addition  of  ammonium  bisulphite  to  prevent 
oxidation. 

Hasmatoxylin  crystallises  with  3  H2O  in  colourless  tetragonal 
prisms  [4],  or  with  1 H2O  in  rhombic  crystals.  It  dissolves 
sparingly  in  cold  water,  and  is  dissolved  with  facility  by  hot  water, 
alcohol,  and  ether.  It  has  a  sweet  taste.  It  melts  in  its  water  of 
crystallisation  somewhat  over  100°.  Its  solution  turns  a  ray  of 
polarised  light  towards  the  right  [3] . 

It  dissolves  in  alkalies  with  a  purple  colour ;  the  colour  rapidly 
changes,  with  formation  of  ha3matem,  to  blue-violet,  afterwards 
becoming  brown.  Chromic  acid,  ferric  chloride,  and  vanadic  acid 
form  higher  oxidation  products,  which  give  black  lakes  with 
metallic  oxides.  On  melting  with  potash,  or  on  dry  distillation, 
it  yields  pyrogallol  and  resorcin  [99] . 

Formic  acid  has  also  been  observed  amongst  the  products 
formed  in  the  potash  melt  [99] . 

Bromine  acts  on  hsernatoxylin  in  acetic  acid  solution,  forming 
a  dibromo  derivative.  Acetic  anhydride  yields  a  pentacetyl 
derivative,  C16H9O6(C2H3O)5,  M.P.  165-166°,  which  on  treating 
with  bromine  combines  with  four  atoms,  and  by  cautious  bromi- 
nation  a  monobromo  derivative  may  be  produced  [6,  13,  99]. 
Nitrous  and  nitric  acid  convert  hsematoxylin  to  hsematem  j  the  final 
product  of  oxidation  with  nitric  acid  is  oxalic  acid. 

Hcematem  [2,  3,  7]. 

Ci6H12O6. 

Hsematem  is  produced  by  careful  oxidation  of  hsematoxylin 
with  nitric  acid  [5],  or  by  action  of  atmospheric  oxygen  on  an 


DYESTUFFS  OF  UNKNOWN  CONSTITUTION.  251 

alkaline  solution  of  this  body  [2,  3].  It  is  best  obtained  by 
exposing  an  ethereal  hsematoxylin  solution  mixed  with  a  few  drops 
of  nitric  acid  to  the  air. 

It  forms  dark  green  masses  with  a  metallic  lustre  or  lustrous 
silvery  leaflets,  which  form  a  red  powder  on  rubbing  [5,  100]. 
It  is  sparingly  soluble  in  hot  water,  alcohol,  and  ether,  forming 
yellowish-brown  solutions.  Its  alkaline  solutions  are  bluish 
violet.  The  ammonia  compound,  C16H12O6,2NH3,  is  sparingly 
soluble  and  evolves  ammonia  on  heating  [3j.  On  treating  with 
aqueous  sulphurous  acid,  hsematein  is  dissolved  without  reduction, 
and  forms  easily  soluble  colourless  addition  compounds,  which  are 
decomposed  on  boiling.  More  stable  compounds  are  obtained 
from  haemate'm  and  bisulphites. 

Hsemate'in  forms  peculiar  addition  products  with  hydrochloric, 
hydrobromic,  and  sulphuric  acids,  which  are  decomposed  by  water 
at  a  high  temperature  [8] . 

In  dyeing  and  printing,  hsematoxylin  and  hsematem  are  used  in 
form  of  logwood  extract  or  decoction. 

Haematoxylin  produces  a  greyish-violet  shade  on  alumina  mor- 
dants, probably  due  to  formation  of  hsematem  by  oxidation. 
Copper  salts  produce  a  dark  blue,  iron  salts  and  chromic  acid  a 
deep  black.  In  practice,  several  of  these  mordants  may  be  applied 
simultaneously;  for  example,  logwood  may  be  printed  on  an 
alumina  mordant  and  afterwards  passed  through  a  bath  of 
potassium  bichromate  or  copper  sulphate.  The  lakes  with  iron 
and  chromium  are  derived  from  higher  oxidation  products  which 
have  as  yet  been  little  examined. 

Logwood  is  largely  used  in  cotton,  wool,  and  silk  dyeing.  For 
wool,  it  serves  especially  for  producing  black  on  iron  and 
chromium  mordants.  The  wool  is  generally  mordanted  in  a  bath 
of  bichromate  and  sulphuric  acid  and  dyed  in  a  logwood  bath. 
Cotton  is  dyed  black  by  alternate  passages  through  logwood  and 
bichromate  baths.  For  production  of  a  deep  black  without  a 
violet  tone,  the  addition  of  fustic  or  a  similar  yellow  dyestuft'  is 
necessary.  A  mixture  used  in  dyeing  and  printing,  under  the 
name  of  indigo  substitute,  is  composed  of  logwood  extract  and 
chromium  acetate. 


252  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Brazilin  [1,  9,  10]. 
Ci6H1405. 

Brazilin  occurs  in  the  wood  of  various  species  of  C&salpinia, 
especially  in  C&salpinia  brasiliensis,  and  with  brazilei'n  forms  the 
essential  constituent  of  the  dye  woods  known  as  Brazil-wood,  Peach- 
wood,  and  Sapan-wood. 

Brazilin  often  separates  from  the  commercial  extract  of  the  dye- 
wood  in  form  of  crystalline  crusts  [9] ,  and  these  are  the  best  material 
for  a  pure  preparation  of  the  compound.  These  crystals  contain 
brazilin  mixed  with  its  calcium  compound,  and  on  boiling  with 
very  dilute  alcohol,  with  a  little  hydrochloric  acid  and  zinc 
powder,  a  solution  is  obtained  from  which  brazilin  crystallises  on 
cooling. 

Brazilin  crystallises  from  water,  according  to  the  concentration 
of  the  solution,  in  clear  amber  rhombic  crystals  containing  1  H2O, 
or  in  colourless  needles  [10]  with  1J  H2O.  It  dissolves  pretty 
easily  in  water,  alcohol,  and  ether.  Alkalies  give  a  carmine-red 
solution,  which  is  decolorised  by  zinc  powder,  the  colour  returning 
quickly  on  exposure  to  air.  On  dry  distillation  it  gives  large 
quantities  of  resorcin  [9] . 

By  action  of  nitric  acid  styphnic  acid  is  formed;  potassium 
chlorate  and  hydrochloric  acid  produce  isotrichlorglyceric  acid  [12] . 

On  adding  lead  acetate  to  an  aqueous  solution  of  brazilin,  the 
lead  compound  separates  in  fine  colourless  needles,  C16H12PbO5 
+  H2O,  which  rapidly  turn  red.  On  reduction  with  hydroiodic  acid 
and  phosphorus,  brazilin  yields  brazinol,  C16H14O4,  and  finally 
C16H26O3,  both  amorphous  bodies  [15].  On  distillation  with  zinc 
powder,  brazinol  gives  a  hydrocarbon  CJ6H14  or  C16H16  [15]. 

Tetracetyl  brazilin, C16H10O5(C2H3O)4  [11],  and  triacetyl  brazilin 
are  formed  by  treating  brazilin  with  acetic  anhydride  [14] . 

Dibrom-  and  dichlorbrazilin  are  formed  by  cautious  bromination 
and  chlorination  of  brazilin  [11,  13]. 

Brazilin  is  applied  technically  in  form  of  extract  or  decoction 
of  brazil-wood.  It  can  be  fixed  only  by  use  of  mordants,  and  is 
used  both  in  cotton  and  wool  dyeing.  On  alumina  mordants  it 
produces  shades  resembling  alizarin,  but  inferior  both  in  beauty 
and  fastness.  The  tin  lake  has  a  brighter  colour.  Wool 
mordanted  with  potassium  bichromate  is  dyed  a  fine  brown 
shade. 


DYESTUFFS  OF  UNKNOWN  CONSTITUTION.  253 

Brazile'in  [11,  12,  7]. 
C16H1205. 

Brazilei'n  bears  the  same  relationship  to  brazilin  that  hsemate'm 
does  to  hsematoxylin.  It  is  formed  by  oxidation  of  an  alkaline 
solution  of  brazilin  in  the  air  and  by  the  action  of  alcoholic  iodine 
solution  [11]  or  of  nitrous  acid  on  the  same  compound. 

Brazilei'n  forms  grey  silvery  leaflets,  which  dissolve  sparingly 
in  water,  easily  in  alkalies  with  a  purple  colour.  Like  hsematein, 
it  forms  unstable  combinations  with  hydrochloric,  hydrobromic, 
and  sulphuric  acids  [8] .  It  resembles  brazilin  from  a  tinctorial 
point  of  view,  but  has  greater  dyeing  power. 

Morin  [1,  16,  15]. 
Ci2H1oO6=C12H8O5  +  H2O. 

Morin  is  the  colouring-matter  of  fustic,  the  wood  of  Morus 
tinctoria  ( Jacq.)  or  Macluria  tinctoria  (Nettel) .  It  is  best  prepared 
by  boiling  the  wood  with  water  and  decomposing  the  lime  com- 
pound with  hydrochloric  acid  [17].  Morin  crystallises  from 
alcohol  in  long  yellow  needles.  It  is  insoluble  in  water  and  carbon 
disulphide,  sparingly  soluble  in  ether,  and  easily  in  alcohol.  It 
dissolves  in  alkalies  with  a  dark  yellow  colour. 

On  dry  distillation  morin  yields  resorcin  and  paramorin.  On 
treatment  with  sodium  amalgam  or  by  melting  with  caustic 
potash  it  yields  phloroglucol,  oxalic  acid  being  also  formed  in  the 
latter  case  [18] . 

Lowe  ascribes  to  morin  the  formula  C15H10O7  +  2H2O  [16]. 

It  acts  as  a  monobasic  acid,  the  salts  of  the  alkali  metals  are 
easily  soluble,  those  with  lime,  aluminium,  lead,  and  zinc  almost 
insoluble  [18]. 

Tribrommorin,  C12H7Br3O6,  is  formed  on  treating  morin  with 
bromine  [18]. 

Paramorin,  C12H8O4,  formed  by  dry  distillation  of  morin,  forms 
yellow  woolly  crystals  easily  soluble  in  water,  and  which  volatilise 
unchanged  [19]. 

Isomorin  [18]  is  formed  by  incomplete  reduction  of  morin 
with  sodium  amalgam.  It  forms  purple-red  prisms,  and  yields 
morin  on  treatment  with  alkali  or  on  heating.  A  compound 
known  as  maclurin  or  morintannic  acid,  C13H10O6,  is  also  contained 
in  fustic,  but  is  not  a  dyestuff. 


254  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Morin  is  used  largely  in  wool  and  cotton  dyeing  as  decoction 
or  extract  of  fustic.  Its  principal  application  is  in  shading  blacks, 
browns,  &c.  Wool  is  generally  mordanted  with  potassium  bichro- 
mate and  sulphuric  acid.  The  morin  is  fixed  as  a  very  stable 
chromium  lake,  which  has  a  dull  yellow  colour. 

Young  fustic,  the  wood  of  Rhus  cotinus,  is  totally  different  from 
old  fustic.  Koch  isolated  the  colouring-matter  [20 J,  termed  it 
fisetin,  and  gave  it  the  formula  C15H10O6.  This  has  been  cor- 
rected by  recent  researches  of  Schmid  [94].  According  to  this 
chemist,  the  colouring-matter  of  young  fustic  occurs  as  a  gluco- 
side  in  combination  with  tannic  acid.  This  tannin  compound  splits 
up  into  the  glucoside,  fustin,  C46H42O21,  and  a  tannic  acid  on  warming 
with  acetic  acid.  The  glucoside  splits  up  with  dilute  acids  into 
sugar  and  fisetin,  C23H10O3(OH)6.  On  boiling  with  acetic  anhydride, 
hexacetyl  fisetin,  C23H10O9(C2H3O)6,  M.P.  200°,  is  produced. 

Hexamethyl  fisetin,  C23H10O9(CH3)6,  is  formed  by  action  of 
methyl  iodide,  M.P.  152°  and  153°. 

The  principal  use  of  fisetin  is  in  wool-dyeing,  especially  for 
modifying  cochineal  scarlets. 

Quercitrin  [1,  21,  22,  24]. 
C36H38O20  +  3H2O. 

Quercitrin  is  the  colouring-matter  of  the  dye  wood  known  as 
quercitron  bark,  obtained  from  Quercus  tinctoria. 

Quercitrin  may  be  obtained  as  follows  : — The  bark  is  boiled 
with  strong  alcohol  and  the  extract  precipitated  with  lead  acetate 
and  acetic  acid.  The  filtrate  is  freed  from  lead  by  sulphuretted 
hydrogen,  and  evaporated.  The  residue  is  crystallised  from  water 
[25] .  It  forms  light  yellow  lustrous  needles,  which  contain  one 
molecule  H2O  after  drying  at  100°,  and  can  be  obtained  an- 
hydrous only  by  long  heating  at  130°  [21] .  It  melts  at  168°  [22] , 
dissolves  sparingly  in  hot  water,  easily  in  alcohol.  Its  solution 
gives  a  green  coloration  with  ferric  chloride.  Ammoniacal  silver 
solution  is  reduced  easily;  Fehling's  copper  solution  only  after 
long  boiling. 

Quercitrin  is  a  diabasic  acid  ;  the  alkali  salts  are  easily  soluble, 
those  with  lead  and  alumina  sparingly  so.  The  former  is  easily 
soluble  in  dilute  sulphuric  acid. 


DYESTUFFS  OF  UNKNOWN  CONSTITUTION.  255 

Quercitrin  is  a  glucoside ;  on  boiling  with  dilute  acids  it  yields 
isodulcite  [24],  C6H]4O6,  and  quercin,  C24H16On.  Quercitrin 
occurs  also  in  hops,  horse-chestnuts,  tea,  and  many  other  plants. 
Tetrabromquercitrin  is  obtained  by  bromination  in  acetic  acid 
solution  and  forms  light  yellow  crystals  [25] . 


Quercitin  [24,  26,  27], 


is  formed  from  quercitrin  as  above,  according  to  the  equation  : 
C36H3802()  4  3H30  =  2C6H14O6  +  C24H16On   [24]  . 

It  also  occurs  naturally  in  many  plants. 

It  forms  fine  lemon-yellow  needles,  sparingly  soluble  in  water, 
but  readily  in  alcohol.  It  melts  above  250°,  and  sublimes  with 
partial  decomposition.  Its  solution  gives  a  green  coloration  with 
ferric  chloride,  which  turns  red  on  heating;  lead  acetate  gives  an 
orange  precipitate.  Silver  nitrate  is  reduced  in  the  cold,  and 
Fehling's  solution  on  warming.  Nitric  acid  oxidises  it  to  oxalic 
acid.  On  fusion  with  caustic  potash,  quercitin  is  split  up,  yielding 
querciglucin,  C6H6O3  (Phloroglucin  ?)  ,  and  quercitic  acid, 
C15H100,  [28]. 

At  a  higher  temperature  protocatechuic  acid  is  formed.  On 
reduction  of  quercitin  the  final  product  is  phloroglucin  [28]  . 

Amide  :  by  action  of  ammonia  at  150°.  Is  a  brown,  amorphous 
compound.  Dibromquercitin  :  light  yellow  needles.  Diacetyl- 
dibromquercitin  :  yellow  needles.  Tetrabromquercitin  :  white 
needles.  M.P.  218°. 

Diacetyltetrabromquercitin  :  white  needles,  M.P.  226-228° 
[25]. 

Quercitin  and  quercitrin  give  beautiful  yellow  shades  on  cotton 
mordanted  with  alumina.  With  tin  mordants  a  more  orange  shade 
is  produced.  On  a  large  scale  these  bodies  have  an  extensive  appli- 
cation, and  are  used  in  form  of  a  decoction  of  the  bark  or  as 
flavin.  In  dyeing  with  the  extract,  it  is  probable  that  the  quer- 
citrin splits  up,  and  that  the  shades  obtained  are  due  to  the  forma- 
tion of  quercitin  lakes. 

Flavin  consists  in  some  cases  of  nearly  pure  quercitrin  and  in 


256  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

others  of  quercitin.  Quercitron  and  flavin  serve  principally  for 
use  with  cochineal  in  dyeing  scarlet.  They  are  also  used  in  calico- 
printing  on  iron,  aluminium,  and  chromium  mordants. 

Rutin,  the  glucoside  contained  in  Chinese  yellow  berries  and  in 
the  leaves  of  Rut  a  graveolens,  is  closely  allied  to  quercitrin.  On 
boiling  with  dilute  acids  it  splits  up  into  quercitin  and  a  sugar 
[29,30,31]. 


Xanthorhamnin,  Ehamnetin  [32,  33,  34]. 

These  colouring- matters  are  contained  in  Persian  berries,  the 
fruit  of  Rhamnus  infectoria  and  oleoides. 

Xanthorhamnin  (or  Rhamnegin)  is  a  glucoside  of  the  compo- 
sition C48H66O29.  It  may  be  obtained  by  extracting  the  berries 
with  alcohol.  Resinous  matters  separate  and  are  filtered  off,  and 
xanthorhamnin  crystallises  out  afterwards.  It  may  be  purified  by 
recrystallisation  from  alcohol  [34];  the  crystals  obtained  contain 
two  molecules  of  alcohol,  which  are  expelled  at  120°.  It  is  very 
easily  soluble  in  water,  less  easily  in  alcohol,  and  insoluble  in  ether 
and  chloroform. 

It  reduces  silver  nitrate  and  Fehling's  copper  solution.  Its 
solution  gives  a  dark  brown  coloration  with  ferric  chloride,  and 
a  yellow  precipitate  with  lead  acetate  and  ammonia.  On  hydro- 
lysis with  dilute  acids  it  gives  rhamnetin  and  isodulcite ;  the  same 
change  may  be  effected  by  simply  heating  to  150°. 

On  acetylation  with  acetic  anhydride  (Schiitzenberger  33),  twelve 
acetyl  groups  enter  into  xanthorhamnin. 


Rhamnetin, 
C12H1005  [34], 

is  formed  along  with  isodulcite,  C6H14O6,  by  hydrolysis  of  xantho- 
rhamnin. It  forms  a  lemon-yellow  powder  sparingly  soluble  in 
water,  alcohol,  ether,  and  indifferent  solvents.  It  is  easily  soluble 
in  phenol,  from  which  it  crystallises  in  yellow  needles.  It  reduces 
ammoniacal  silver  solution  and  Fehling's  copper  solution. 

Its  aqueous  solution  gives  yellow  or  brownish-yellow  precipitates 


DYESTUFFS  OF  UNKNOWN   CONSTITUTION.  257 

with  lead,  alumina,  barium,  and  lime-salts.  On  fusion  with 
potash,  or  reduction  with  sodium  amalgam,  rhamnetin  yields 
phloroglucin  and  protocatechuic  acid. 

Dimethylrhamnetin  is  formed  by  heating  rhamnetin  with  potas- 
sium-methylsulphate,  and  methyl  alcohol  to  120°,  M.P.  157°  [34]. 

Herzig  has  recently  found  that  the  highest  products  obtained 
by  methylation  of  rhamnetin  and  quercitin  are  identical,  and  has 
further  obtained  quercitin  by  removal  of  a  methyl  group  from 
rhamnetin  with  hydriodic  acid.  From  these  results  he  regards 
rhamnetin  as  a  dimethylquercitin. 

Diacetylrhamnetin,  M.P.  185°  [34]. 

Dipropionylrhamnetin,  M.P.  162°  [34], 

Dibenzoylrhamnetin,  M.P.  210^212°. 

These  three  compounds  are  obtained  by  action  of  the  respective 
anhydrides  on  rhamnetin  [34] . 

Dibromrhamnetin,  obtained  by  bromination  of  rhamnetin  in 
acetic  acid  solution,  forms  yellow  needles  soluble  in  hot  benzene, 
alcohol,  and  acetic  acid  [34] . 

Diacetyldibromrhamnetin  is  formed  by  bromination  of  diacetyl- 
rhamnetin,  M.P.  212°  [34]. 

Xanthorhamnin  is  not  a  dyestuff,  and  it  must  therefore  be 
accepted  that  rhamnetin  is  formed  in  the  dyeing  operations. 

Rhamnetin  in  form  of  Persian-berry  extract  is  of  considerable 
importance  in  calico-printing ;  no  artificial  dyestuff  has  been  found 
to  replace  it  with  advantage.  It  is  generally  fixed  as  tin  or  tin- 
alumina  lake,  both  of  which  have  a  fine  yellow  colour.  The 
chromium  lake  has  a  browner  tone  and  is  also  used  in  printing. 
The  alumina  lake  also  sometimes  used  in  dyeing  has  lemon  shade  ; 
its  principal  application  (mixed  with  chalk)  is  as  an  artists'  colour. 

Persian  berries  also  contain  rhamnin  or  /3-rharnnegin,  which 
yields  fi- rhamnetin  on  hydrolysis  [39].  The  composition  of  these 
bodies  is  unknown. 


Luteolin  [1,  36,  37,  38]. 

C12H8O5. 

Luteolin  is  the  colouring-matter  of  weld,  the  leaves  and  skin  of 
Reseda  luteola.     Luteolin  crystallises  from  alcohol  in  small  yellow 


258  CHEMISTRY  OF  ORGANIC  DYESTTJFFS. 

needles  which  contain  1J  molecules  of  water  of  crystallisation, 
which  are  expelled  at  150°  [38].  It  melts  at  320°  [36]  and  may 
be  sublimed  with  partial  decomposition.  It  is  very  sparingly 
soluble  in  water  and  ether;  alcohol  dissolves  it  with  tolerable 
facility. 

It  dissolves  readily  in  alkalies  with  a  yellow  colour,  and  gives 
yellow  lakes  with  lead  and  alumina  salts. 

Ferric  chloride  produces  a  green  coloration,  changing  to  brown 
with  excess  of  the  reagent. 

On  fusion  with  potash,  luteolin  yields  phloroglucin  and  photo- 
catcchuic  acid  [37] . 

Luteolin  is  obtained  by  extracting  weld  with  dilute  alcohol, 
evaporating  the  extract,  and  recrystallising  the  compound  which 
separates. 

An  aqueous  decoction  of  weld  is  used  in  dyeing.  On  alumina 
mordants  it  produces  a  beautiful  fast  yellow.  Its  principal 
application  is  in  silk-dyeing,  for  which  weld  is  a  valuable  material. 
Silk  is  previously  mordanted  with  alum. 


Bixin  [48,  49,  50,  51], 


Bixin  is  the  principal  colouring-matter  contained  in  annatto. 
This  dyeware  consists  chiefly  of  the  pulp  of  the  fruit  of  Bixa 
orellana  which  has  been  allowed  to  ferment. 

Bixin  is  prepared  by  boiling  annatto  with  alcohol  and  sodium 
carbonate.  On  adding  soda  solution  to  the  extract,  the  sodium 
compound  of  bixin  separates;  this  is  purified  by  recrystallising  from 
dilute  alcohol,  and  the  bixin  liberated  by  hydrochloric  acid  [51]. 

Bixin  forms  dark  red  metallic  leaflets,  M.P.  176°.  It  is  almost 
insoluble  in  water,  sparingly  soluble  in  cold  alcohol,  benzene, 
glacial  acetic  acid,  arid  ether,  readily  soluble  in  hot  alcohol  and 
in  chloroform.  Bixin  is  a  dibasic  acid.  It  reduces  Fehling's 
solution  in  the  cold.  It  forms  a  blue  solution  with  concentrated 
sulphuric  acid,  whHch  gives  a  dirty  green  precipitate  on  addition  of 
water.  Sodium  amalgam  converts  it  to  a  colourless  compound, 
C28H40O5  [51].  On  oxidation  with  nitric  acid,  bixin  yields  oxalic 
acid.  On  distillation  with  zinc  powder,  it  yields  metaxylene, 
meta-ethyl  toluene,  and  a  hydrocarbon  C14H14,  ?  [51]. 


DYESTUFFS  OF  UNKNOWN   CONSTITUTION.  259 

Bixin  gives  two  sodium  salts:  NaC28H33O5  +  H2O,  forming 
coppery-red  crystals,  and  Na2C28H32O5,  a  red  powder  [51]. 

Annatto  contains  a  second  colouring-matter  known  as  Orellin, 
the  composition  of  which  is  unknown.  It  dyes  a  yellow  shade  on 
alumina  mordants,  and  is  probably  an  oxidation  product  of  bixin. 

Bixin  dyes  both  animal  and  vegetable  fibres  without  a  mordant. 
It  is  used  both  in  silk  and  cotton  dyeing  in  form  of  annatto.  It 
is  either  fixed  directly  on  cotton,  or  in  form  of  its  tin  lake,  the 
result  being  a  fine  orange-yellow  shade.  Annatto  has  a  large 
application  in  colouring  butter  and  cheese. 


Chrysin  [52 


Chrysin  occurs  in  the  buds  of  the  poplar  (Populus  balsamifera 
and  monilifera)  .  It  forms  light  yellow  needles,  M.P.  275°,  insoluble 
in  water,  sparingly  soluble  in  benzene,  ligroin,  and  cold  alcohol, 
easily  in  glacial  acetic  acid,  aniline,  and  hot  alcohol.  It  dissolves 
in  alkalies  with  a  yellow  colour.  Its  alcoholic  solution  is  coloured 
dirty  violet  by  ferric  chloride,  and  gives  a  yellow  precipitate  with 
lead  acetate.  Chrysin  is  decomposed  on  boiling  with  concentrated 
potash  solution,  forming  acetophenone,  acetic  acid,  benzoic  acid, 
and  phloroglucin.  On  heating  with  methyl  iodide  it  yields 
a  monomethylether  (tectochrysin)  ,  C15H9O3OCH3,  which  also 
occurs  in  poplar-buds.  It  forms  thick  sulphur-yellow  crystals, 
M.P.  164°.  It  is  insoluble  in  alkalies,  sparingly  soluble  in 
alcohol,  and  easily  in  benzene. 

Nitrochrysin,  C15H9NO2O4,  is  formed  by  action  of  nitric  acid  on 
chrysin. 

Dibromchrysin,  C15H8Br2O4. 

Diiodochrysin,  C15H8I2O4. 


Curcumin  [53,  54,  55,  56]. 

C14H1404? 

This  slightly  acid  colouring-matter  is  contained  in  turmeric, 
the  underground  stem  of  Curcuma  longa  and  C.  viridiflora. 

s2 


260  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Curcumin  is  prepared  by  steaming  turmeric,  or  extracting  with 
carbon  bisulphide  to  remove  oily  matters,  and  extracting  the 
residue  with  ether.  The  crude  product  is  purified  by  recrystal- 
lisation  from  ether  or  benzene.  It  forms  orange-yellow  prisms, 
M.P.  178°  [56] .  It  is  very  sparingly  soluble  in  hot  water,  more 
easily  in  benzene,  and  readily  in  alcohol,  ether,  and  fatty  oils.  It 
dissolves  in  alkalies  with  a  brown  colour,  and  also  gives  a  brown 
coloration  with  boric  acid,  changing  to  blue  on  addition  of  dilute 
alkali  [53].  (Reaction  for  boric  acid.)  It  gives  insoluble  brown 
lakes  with  lead  calcium  and  barium  salts.  It  dissolves  in  concen- 
trated sulphuric  acid  with  a  cherry-red  colour. 

Nitric  acid  oxidises  curcumin  to  oxalic  acid ;  chromic  acid 
produces  terephthalic  acid  [54]. 

Curcumin  is  extensively  used  in  dyeing,  although  not  fast  to 
light.  Its  principal  application  is  in  modifying  red  shades  on 
cotton,  for  example  saffranine.  Curcumin  dyes  cotton  without 
mordant.  The  powdered  root  is  generally  used  suspended  in 
water.  The  cotton  is  boiled  in  a  mixture,  and  the  curcumin 
becomes  fixed  as  it  dissolves.  An  alcoholic  extract  is  sometimes 
used,  and  is  mixed  with  water  to  an  emulsion.  Turmeric  is  also 
used  for  colouring  butter,  wax,  and  fatty  oils. 


Carotin  [57,  58,  59], 
Ci8H24O. 

Carotin  is  the  colouring-matter  contained  in  the  carrot  (Daucus 
carota).  It  forms  rhombic  crystals,  M.P.  168°,  reddish  brown  in 
transmitted  light,  and  gold  green  by  reflected  light.  It  is  easily 
soluble  in  carbon  disulphide,  sparingly  in  alcohol  and  ether. 
It  gives  a  violet  solution  with  strong  sulphuric  acid,  and  is  coloured 
blue  by  sulphurous  acid.  Arnaud  [96]  regards  carotin  as  a  hydro- 
carbon, but  this  assumption  is  extremely  improbable  from  the 
properties  of  the  compound. 

Archil  and  Litmus. 

Various  kinds  of  lichens,  for  example  Lecanora  tinctoria  and 
Roccella  tinctoria,  possess  the  property  of  giving  violet  or  blue  dye- 
stuffs  when  submitted  to  the  joint  action  of  ammonia  and  air. 


DYESTUFFS  OF  UNKNOWN  CONSTITUTION.  261 

These  lichens  contain  a  number  of  peculiar  acids  (lecanoric  acid, 
erythric  acid,  roccellic  acid,  &c.),  which  are  split  up  by  alkalies, 
the  final  products  being  orcin,  C6H3CH3(OH)2,  and  erythrite, 
C4H10O4. 

Orcin  is  the  only  compound  important  for  the  production  of 
lichen  colours;  with  air  and  ammonia  it  yields  orcei'n,  C7H7NO3?, 
which  is  the  principal  dyestuff  contained  in  archil  [60,  61,  62,  63] . 

Orcei'n  gives  sparingly  soluble  lakes  with  calcium  and  the 
heavy  metals,  but  does  not  appear  to  be  a  real  adjective  dyestuff. 

Commercial  archil  is  prepared  by  moistening  the  weeds  with 
ammonia  and  exposing  the  mixture  to  the  air.  Formerly  putrid 
urine  was  used  in  place  of  the  ammonia.  The  product  obtained 
may  be  worked  up  into  extract,  "Archil  liquor;  "  or  dried  and 
powdered,  or  is  sold  in  the  crude  form  as  "  Archil  paste."  These 
products  all  contain  orcei'n  in  form  of  its  ammonia  salt. 

The  dyeware  known  as  Cudbear  is  similar  to  powdered  archil. 
Besides  orcei'n,  archil  is  said  to  contain  two  other  colouring- 
matters  of  unknown  composition,  azoerythrin  and  erythroleic 
acid  [60]. 

Archil  is  principally  employed  in  wool  and  silk  dyeing,  less  in 
calico-printing.  It  may  be  dyed  on  wool  from  acid,  neutral,  or 
alkaline  baths.  An  addition  of  alum,  stannous  chloride,  oxalic 
acid,  or  tartaric  acid  is  made  to  the  dyebath. 

The  calcium  lake  is  used  in  printing,  and  is  dissolved  in  acetic 
acid  and  fixed  by  steaming  (" French  purple").  The  shades 
obtained  with  archil  are  purple,  and  may  be  modified  with  indigo 
or  cochineal. 

Archil  has  been  displaced  to  a  certain  extent  by  azo  dyestuffs, 
but  still  has  considerable  importance  in  wool-dyeing.  This,  is  due 
to  the  various  conditions  under  which  archil  may  be  employed, 
and  it  can  therefore  be  used  to  modify  the  shades  of  nearly  all 
other  dyestuffs. 


Litmus. 

If  the  lichens  used  for  the  manufacture  of  archil  are  submitted 
to  a  longer  treatment  with  ammonia,  potash  and  lime  being  also 
added,  the  orcin  is  converted  to  litmus — a  dyestuff  which  is  red 
in  the  free  state,  and  yields  blue  salts.  A  similar  product  may  be 


262  CHEMISTRY  OF  ORGANIC  DYESTU1TS. 

obtained  direct  from  orcin  by  continued  digestion  with  a  mixture 
of  ammonia  and  soda  solution  [64] . 

Litmus  comes  into  commerce  in  small  tablets  mixed  with  chalk 
or  gypsum,  the  commercial  product  containing  only  a  small 
quantity  of  dyestuff. 

Litmus  is  best  known  as  an  indicator  in  volumetric  analysis,  but 
is  also  used  to  inconsiderable  extent  for  colouring  wine  and  for 
blueing  in  laundries. 

According  to  Kane  (60), litmus  contains  four  colouring-matters — 
Erythrolein,  Azolitmin,  Erythrolitmin,  and  Spaniolitmin — the  first 
two  being  the  most  important.  It  is  improbable,  however,  that 
these  compounds  are  chemical  individuals. 

According  to  Wartha  (61),  some  kinds  of  litmus  contain  indigo. 

Carthamin  [62], 
CWH1707(?). 

Safflower,  the  petals  of  Carthamus  tmctorius,  &c.,  contains, 
besides  a  yellow  dyestuff,  a  red  one,  carthamine,  which  was  of 
considerable  importance  before  the  introduction  of  the  artificial 
dyestuffs. 

To  prepare  carthamin,  safflower  is  washed  with  water  to  remove 
the  yellow  dyestuff,  and  is  then  extracted  with  dilute  soda  solution, 
and  filtered.  Cotton  yarn  is  immersed  in  the  alkaline  solution, 
and  the  liquid  acidulated  with  citric  acid.  The  cotton  takes  up 
the  carthamin,  which  is  removed  with  soda  solution,  and  pre- 
cipitated with  citric  acid.  Obtained  in  this  manner  carthamin 
forms  a  lustrous  green  powder,  sparingly  soluble  in  water  and  ether, 
readily  in  alcohol.  It  dissolves  in  alkalies  with  yellowish-green 
colour.  On  fusion  with  potash  it  gives  oxalic  acid  and  para-oxy- 
benzoic  acid.  Carthamin  dyes  animal  fibres  and  unmordanted 
cotton  from  a  slightly  acid  bath.  It  produces  a  beautiful  pink 
colour  on  silk. 

Cartharain  enters  commerce  in  a  nearly  pure  state  as  saf- 
flower extract.  For  dyeing,  the  extract  is  dissolved  in  soda  and  the 
dyebath  acidified  with  citric  or  other  acid.  In  place  of  this 
extract  the  soda  solution  from  safflower,  which  has  been  extracted 
with  water,  may  be  directly  employed. 

Carthamin  is  also  used  as  rouge  in  admixture  with  talc,  chalk, 
or  starch.  It  is  also  employed  as  an  artists'  colour. 


DYESTUFFS  OF  UNKNOWN  CONSTITUTION.  263 

The  yellow  colouring-matter  of  safflower,  which  according  to 
Malin  has  the  composition  C24H30O15  [63],  is  of  no  importance  in 
dyeing. 

Santalin  [64,  65,  66]. 

Sandal-wood  or  Sanders- wood  (from  Pterocarpus  santalinus) 
contains  a  resinous  red  dyestuff  of  slightly  acid  properties. 
Santalin,  C15H14O5,  is  obtained  by  precipitating  an  alcoholic  extract 
of  sandal-wood  with  lead  acetate,  and  decomposing  the  lead  lake 
with  dilute  sulphuric  acid.  It  crystallises  from  alcohol  in  red 
prisms,  M.P.  104°.  It  is  sparingly  soluble  in  water,  dissolves  in 
alcohol  and  ether  with  a  blood-red  colour,  and  in  alkalies  with  a 
violet  colour.  It  gives  violet  insoluble  lakes  with  calcium,  barium, 
and  the  heavy  metals. 

Franchimont  [67],  who  could  obtain  santalin  only  in  an  amor- 
phous state,  ascribes  to  it  the  formula  C17H16O6.  On  heating  with 
hydrochloric  acid  to  200°,  he  obtained  methyl  chloride  and  an 
amorphous  body  (C8H19O5  ?),  which  gives  a  violet-black  solution 
with  alkalies. 

Santalin  is  largely  used  in  wool-dyeing  and  is  employed  as 
rasped  sanders-wood,  which  is  directly  added  to  the  dyebath.  It 
produces  a  good  reddish-brown  shade  on  chromed  wool,  which  is, 
however,  not  very  fast  to  light. 

An  alcoholic  extract  of  sanders-wood  is  also  used  for  colouring 
tinctures,  varnishes,  and  also  for  staining  wood. 


Alkannin  [70], 


Alkanet,  the  root  cf  Anchusa  iinctoria,  contains  the  above  red 
dyestuff.  It  is  of  slightly  acid  character,  and  has  not  been  obtained 
in  a  crystalline  state.  It  is  insoluble  in  water,  dissolves  easily  in 
alcohol,  ether,  ligroin,  and  fatty  oils,  forming  red  solutions.  It 
dissolves  in  alkalies  with  a  blue  colour,  and  is  reprecipitated  by  acids 
in  red  flakes.  It  gives  an  insoluble  lake  with  baryta.  It  is  pro- 
bably a  derivative  of  methylanthracene,  C15H12,  as  it  yields  this 
hydrocarbon  on  distillation  with  zinc  powder  [93]  . 

The  diacetyl  compound,  C15H12(C2H3O)2O4,  is  formed  by  the 
action  of  acetic  anhydride  and  sodium  acetate  [70]. 


264  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Alkannin  dissolves  in  concentrated  sulphuric  acid  with  a  blue 
colour.  Nitric  acid  oxidises  it  to  oxalic  acid  and  succinic  acid. 

Alkannin  (in  form  of  an  extract  of  alkanet  root)  is  used  for 
colouring  oils,  pomades,,  tinctures.,  &c. 


Crocin  and  Crocetin. 

Saffron,  the  stigmata  of  Crocus  sativus,  contains  according  to 
Quadrat  [71]  and  Weiss  [72]  a  yellow  glucoside,  polychroite, 
C48H68O18  [73].  According  to  these  chemists  it  may  be  split  up 
into  crocin,  C16H18O6,  sugar,  and  an  ethereal  oil. 

R.  Kayser  [74]  terms  poly chroit "  crocin,"  and  crocin  "crocetic," 
and  ascribes  to  the  former  the  formula  C44H70O28,  and  to  the  latter 
C34H46O9.  According  to  him,  crocin  splits  up  into  crocetin  and 
saffron  sugar,  C6H1206,  while  the  ethereal  oil  is  a  product  of  the 
decomposition  of  picrocrocin. 

L.  Meyer  [73]  and  "Rochleder  obtained  crocin  from  the  pods  of 
Gardenia  grandiflora,  but  it  is  not  certain  whether  their  product  is 
identical  with  the  above.  They  obtained  a  glucoside,  C58H86O31, 
which  splits  up  into  sugar  and  crocetin,  C34H36O4.  As  these  bodies 
were  only  obtained  in  an  amorphous  state,  these  formulae  appear 
to  be  doubtful. 


Lo-Kao  (CHINESE  GKEEN). 

The  above  is  a  commercial  green  dyestuff  prepared  from  the  bark 
of  various  species  of  Ehamnus  (Rhamnus  utilis,Rh.  chlorophlorus] . 
It  consists  chiefly  of  the  alumina  and  lime  lakes  of  the  glucoside. 

This  latter  is  termed  loka'in  by  Cloez  and  Guignet  [75],  and 
lokaonic  acid  by  Kayser  [76]. 

According  to  Cloez  and  Guignet  a  compound  has  the  formula 
C28H34O17,  and  is  decomposed  by  acids,  yielding  glucose  and 
lokaetin,  C9H8O5  [75] .  Kayser,  on  the  other  hand,  gives  to  lokai'n 
(lokaonic  acid)  the  formula  C42H48O27,  and  to  lokaetin  (lokanic 
acid)  the  formula  C36H36O21.  The  sugar  produced  in  the  formation 
of  the  latter  is  not  glucose,  but  an  inactive  modification  which 
Kayser  terms  Lokaose.  Lokam  forms  a  deep  bluish-black  mass 
which  takes  a  metallic  lustre  on  rubbing.  It  is  insoluble  in  water, 
alcohol,  ether,  chloroform,  and  benzene,  but  soluble  in  alkalies 
with  a  blue  colour,  which  is  changed  to  red  by  reducing  agents. 


DYESTUFFS  OF  UNKNOWN  CONSTITUTION.  265 

The  ammonium  salt  forms  lustrous  bronzy  crystals.  The  other 
salts  are  amorphous ;  those  of  the  heavy  metals  are  insoluble. 

Lokaetin  (lokanic  acid)  forms  a  violet-black  powder  only  soluble 
in  alkalies,  with  a  violet  colour. 

According  to  Kayser  it  reacts  with  sulphuretted  hydrogen, 
forming  a  crystalline  compound  containing  sulphur. 

Concentrated  sulphuric  acid  produces  a  brown  amorphous  com- 
pound, which  is  stated  to  be  C7H6O4  by  Cloez  and  Guignet,  and 
C36H26O16  by  Kayser. 

The  formulae  for  the  compounds  described  above  must  be  re- 
garded as  doubtful,  as  the  nature  of  the  substances  affords  little 
guarantee  for  their  purity,  and  the  analysis  gives  little  idea  of  the 
true  size  of  the  molecules. 

Lo-kao  is  used,  especially  by  the  Chinese,  for  dyeing  wool  and 
silk.  It  may  be  fixed  on  cotton  from  an  alkaline  bath,  but  is  also 
frequently  used  in  a  reduced  state  as  a  vat,  stannous  chloride  or 
ammonium  sulphide  being  used  as  reducing  agents.  The  shade 
produced  is  a  fine  bluish  green,  very  fast  to  light. 

Cochineal. 

The  important  dyeware  known  as  cochineal  consists  of  the  dried 
female  of  an  insect,  the  Coccus  cacti  coccinellifera,  which  lives  on 
certain  species  of  cactus.  The  colouring  principle  of  cochineal  is 
glucoside  carminic  acid,  of  the  formula  C17H16O10  [77]. 

Carminic  acid  is  prepared  by  precipitating  an  aqueous  decoction 
of  cochineal  with  lead  acetate,  and  decomposing  the  lead  lake  with 
a  quantity  of  sulphuric  acid  insufficient  for  the  whole.  The 
solution  of  carminic  acid  thus  obtained  is  evaporated  to  dryness  at 
a  low  temperature,  and  the  residue  crystallised  from  absolute 
alcohol. 

Obtained  in  this  manner,  carminic  acid  forms  a  purple-brown 
mass  which  gives  a  scarlet  powder  on  trituration.  It  is  with  diffi- 
culty soluble  in  ether,  easily  in  water  and  alcohol. 

It  is  a  weak  dibasic  acid,  forming  violet  salts ;  those  with  the 
alkalies  are  easily  soluble,  with  the  earths  and  heavy  metals  they 
are  insoluble.  The  sodium  salt  may  be  crystallised;  the  other 
salts  are  amorphous. 

On  boiling  with  dilute  acids,  carminic  acid  is  split  up  into 
carmine-red,  CnH12O7,  and  a  sugar,  C6H10O5.  In  general,  car- 


266  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

minic  acid  gives  the  same  decomposition  products  as  carmine-red. 
If  an  ammoniacal  solution  is  allowed  to  stand,  a  nitrogenous 
compound  is  formed,  possessing  totally  different  dyeing  properties. 
On  a  large  scale  this  product  is  prepared  for  dyeing  by  maceration 
of  ground  cochineal  with  ammonia,  and  is  used  under  the  name  of 
ammoniacal  cochineal. 

In  dyeing,  this  product  gives  much  bluer  shades,  and  is  used  for 
modifying  cochineal  scarlets. 

Carmine-red. 
CnH12O7. 

Carmine-red  is  prepared  from  the  lake  obtained  by  precipitating 
a  cochineal  decoction  with  lead  acetate.  This  lead  lake  is  dis- 
solved in  dilute  sulphuric  acid,  freed  from  lead  by  sulphuretted 
hydrogen,  and  boiled  with  very  dilute  sulphuric  acid  for  some 
hours.  Barium  carbonate  is  added  till  a  violet  coloration  ensues, 
and  then  filtered  rapidly  and  precipitated  with  lead  acetate.  The 
lead  lake  is  decomposed  and  the  nitrate  evaporated  to  dryness  in 
vacuo. 

Carmine-red  is  a  dark  red  substance,  which  appears  green  by 
reflected  light.  It  is  insoluble  in  ether,  but  soluble  in  water  and 
alcohol  with  a  red  colour.  Keducing  agents  convert  it  to  a  colour- 
less compound.  On  fusion  with  potash  carminic  acid  yields  coccinin 
[80]  ,  and  on  heating  with  water  to  200°  ruficarmine  is  formed  [82]  . 

By  boiling  carminic  acid  with  nitric  acid,  trinitrococcussic  acid 
(trinitrocresotinic  acid)  , 

OH 


is  formed  [78]  . 

Bromine  reacts  with  carminic  acid,  producing  two  brominated 
compounds,  a-bromcarmine,  C10H4Br4O3  [81],  forms  colourless 
needles,  M.P.  248°,  which  are  soluble  in  alkalies.  On  boiling  with 
strong  potash  solution  it  yields  oxybromcarmine,  which  behaves 
like  an  oxyacid  of  the  formula 


DYESTUFFS  OF  UNKNOWN  CONSTITUTION.  267 

On  oxidation  with  potassium  permanganate,  oxybromcarmine 
yields  an  acid  of  the  formula  C9H6Br2O4,  probably  dibromoxy- 
tolylformic  acid,  C7H5OBr2COCOOH.  Dibrommethoxylmethyl- 
phthalic  anhydride, 

^OCR, 
CH3 — C6Br2-COXQ 

is  also  formed  [81]. 

/3-bromcarmine,  Cl}Ji5Br3iO4f  forms  yellow  needles,  M.P.  232°, 
and  gives  red  dibasic  salts  with  the  alkalies. 

On  oxidation  with  potassium  permanganate  it  yields  dibrom- 
oxymethylbenzoyldicarbonic  acid, 

,COOH 


and  the  above  dibrommethoxymethylphthalic  anhydride  [81]. 

Ruficoccin,  C16H10O6,  is  formed  along  with  a  compound  of  the 
composition  C32HooO13  by  heating  carmine-red  with  sulphuric  acid 
to  130-140°  [82~f. 

Ruficoccin  is  a  brick -red  powder,  sparingly  soluble  in  water  and 
ether,  easily  soluble  in  alcohol.  It  dissolves  in  alkalies  with  a 
brown  colour.  On  distillation  with  zinc  powder  a  hydrocarbon, 
C16H12,  is  formed  [82]. 

Ruficarmine  [82J  forms  a  carmine-red  powder  insoluble  in 
water,  but  easily  soluble  in  alcohol. 

Carmine-red  is  a  dibasic  acid,  and  forms  salts  similar  to  those  of 
carminic  acid. 

Coccinin,  C14H12O5  [80] ,  is  formed  on  melting  carminic  acid  or 
carmine-red  with  potash.  It  forms  yellow  leaflets,  insoluble  in 
water,  but  soluble  in  alcohol  and  alkalies.  The  alkaline  solution 
becomes  oxidised  on  exposure  to  the  air,  the  colour  changing 
through  green  to  red.  A  solution  of  coccinin  in  concentrated 
sulphuric  acid  gives  a  blue  coloration  on  addition  of  manganese 
dioxide. 

Carmine. — This  is  a  commercial  product  made  from  cochineal, 
which  is  used  by  artists  and  for  colouring  confectionery,  and  also 
as  rouge.  Carmine  forms  porous  red  masses,  which  are  easily 
rubbed  to  fine  powder.  It  is  insoluble  in  water  and  alcohol,  but 
dissolves  completely  in  ammonia  if  free  from  adulteration  with 
kaolin,  starch,  &c. 


268  CHEMISTRY  OF  ORGANIC  DYESTUFF8. 

The  exact  method  employed  for  this  preparation  is  unknown ; 
various  recipes  are  in  vogue,  according  to  which  the  essential 
consists  in  precipitating  an  aqueous  decoction  of  cochineal  with 
alum.  According  to  the  researches  of  Liebermann  [83]  carmine 
contains  about  3  per  cent,  of  alumina  and  about  the  same  quantity 
of  lime,  and  also  about  20  per  cent,  of  albuminoid  matters. 

As  the  lime  and  alumina  dissolve  in  ammonia  and  cannot  be 
detected  therein  by  the  ordinary  reagents,  it  is  probable  that  a 
peculiar  lake  of  carmine-red  is  present,  in  which  the  albuminoids 
play  a  part. 

The  colour  of  carmine,  and  especially  that  of  its  ammoniacal 
solution,  differ  considerably  from  that  of  carmine-red. 

The  above  ammoniacal  solutions  were  formerly  used  as  red  ink. 

Cochineal  is  employed  in  dyeing  for  production  of  scarlet  shades. 
Before  the  introduction  of  the  red  azo-dyestuffs  cochineal  was  the 
only  material  which  could  be  used  for  scarlets,  but  recently,  owing 
to  competition  with  the  artificial  dyestufPs,  its  use  has  greatly 
diminished.  Neither  carminic  acid  nor  carmine-red  can  be  fixed 
without  mordant.  The  finest  scarlet  tones  are  obtained  with  the 
tin  lake  of  carminic  acid,  or  probably  of  the  carmine-red  formed 
by  its  decomposition. 

In  dyeing  wool  scarlet,  the  mordanting  and  dyeing  operations 
are  generally  carried  out  in.  one  bath,  the  material  being  boiled 
with  ground  cochineal  and  stannous  chloride,  an  addition  of  tartar 
or  oxalic  acid  being  generally  made.  Yellower  shades  are  obtained 
by  addition  of  weld,  flavine,  or  fustic. 

The  alumina  lake  has  violet  colour,  and  the  iron  a  blackish- grey. 
Owing  to  the  latter,  it  is  important  to  have  water  mordants,  &c., 
perfectly  free  from  iron  in  dyeing  cochineal  scarlet. 

Ammoniacal  cochineal  produces  bluer  shades  on  tin  mordants. 
Cochineal  is  seldom  used  in  cotton-dyeing.  Cochineal  lakes  are 
often  used  in  printing,  being  mixed  with  albumen  and  fixed  by 
steaming.  The  artists'  colour  known  as  Florentine  lake  is  prepared 
"by  precipitating  a  decoction  of  cochineal  with  alum  and  soda  or 
chalk.  It  contains  the  alumina  lake  of  carminic  acid,  mixed  with 
excess  of  alumina  and  chalk. 


DYESTUFFS  OF  UNKNOWN  CONSTITUTION.  269 

Lac-dye. 

Lac-dye  is  also  a  product  of  a  species  of  Coccus,  the  Coccus 
lacca  or  C.  ficus.  These  insects  live  on  the  branches  of  Ficus 
religiosa  and  Ficus  indica.  A  resinous  matter  exudes  from  the 
tree  and  envelopes  the  insects.  The  twigs  are  cut  off  along  with 
the  resin,  and  sold  as  stick-lac.  On  treating  stick-lac  with  water, 
the  colouring-matter  dissolves,  and  the  residue,  melted  and  squeezed 
through  calico,  forms  commercial  shellac.  The  exact  method  by 
which  commercial  lac-dye  is  prepared  is  kept  secret,  but  it  probably 
consists  in  precipitation  of  an  alkaline  decoction  of  stick-lac  with 
alum. 

The  colouring-matter  contained  in  lac-dye  was  long  considered  to 
be  identical  with  that  of  cochineal,  but,  as  shown  by  the  researches 
of  R.  E.  Schmidt  [95],  it  is  a  new  body,  laccainic  acid,  C16H12O8. 

Lac-dye  is  used  in  dyeing  in  a  similar  manner  to  cochineal,  the 
principal  difference  being  that  it  requires  a  very  acid  bath.  The 
shades  produced  are  not  so  clear  as  those  of  cochineal,  but  surpass 
the  latter  in  fastness  both  to  light  and  alkalies. 

Kermes,  another  insect  (Coccus  ilicis,  C.  baphia),  contains 
analogous  colouring-matters,  and  was  formerly  used  in  dyeing, 
but  has  now  gone  out  of  use. 

Other  insects,  for  example  Coccus  polonicus,  C.fragaria,  contain 
red  dyestuffs. 

Colouring-matter  of  Tynan  Purple  [84,  85]. 

Certain  molluscs  (Purpura  lapillus,  P.  hamastoma,  and  various 
species  of  Murex),  when  crushed  and  exposed  to  sunlight,  develop 
a  purple  dyestuff  which  was  highly  prized  by  the  ancients. 
According  to  Schunck  [84]  the  dyestuff,  punicine,  is  insoluble  in 
water,  alcohol,  and  ether,  slightly  soluble  in  benzene  and  glacial 
acetic  acid,  and  easily  soluble  in  aniline  and  concentrated  sul- 
phuric acid  [85].  It  sublimes  with  partial  decomposition  in 
leaflets,  which  have  a  metallic  lustre. 

Witt  regards  this  dyestuff  as  indigo  mixed  with  a  red  dyestuff 
less  fast  to  light.  On  ancient  purple  cloth  this  red  has  been 
bleached  in  course  of  time,  and  only  the  blue-indigo  ground 
remains.  Compare  Witt  [98] . 


270  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


Catechu. 

The  commercial  products  known  as  Catechu  and  Cutch  are 
prepared  by  evaporation  of  aqueous  extracts  of  the  wood  of  Acacia 
catechu  and  allied  species,,  common  in  India.  Gambier  is  a  similar 
preparation ;  its  exact  composition  has  not  been  investigated. 
Catechu  serves  technically  both  as  a  colouring-matter  and  as  a 
tannin,  and  is  largely  employed  in  cotton-dyeing  and  in  tanning. 

The  principal  constituents  of  catechu  are  catechin  and  catechu- 
tannic  acid. 

Catechin. — On  treating  catechu  with  cold  water,  catechu-tannic 
acid  dissolves,,  and  the  catechin  contained  in  the  residues  may  be 
obtained  by  extraction  with  boiling- water.  Catechin  separates 
from  the  solution  on  cooling,  and  may  be  purified  by  recrystal- 
lising  from  boiling-water.  It  forms  minute  white  needles,  M.P. 
217°,  which  are  sparingly  soluble  in  cold  water,  readily  in  alcohol 
and  in  boiling-water.  Catechin  yields  pyrocatechin  and  phloro- 
glucin  on  heating  with  dilute  sulphuric  acid  under  pressure.  It 
does  not  precipitate  solutions  of  gelatine,  tartar-emetic,  or  alka- 
loids, thus  differing  from  the  tannins. 

There  is  some  uncertainty  as  to  the  exact  composition  of 
catechin.  Liebermann  and  Tauchert  give  the  formula 

C21H2009  +  5H20 

as  most  probable,  and  they  have  also  analysed  a  diacetyl  com- 
pound, M.P.  128°-130°,  which  supports  this  formula  [105]. 

Etti  ascribes  to  catechin  the  formula  C38H36O16,  and  uses  this  ia 
the  following  series  of  anhydrides  described  by  him  [106] . 

By  the  action  of  heat,  or  of  dilute  acids,  catechin  gives  rise  to  a 
series  of  anhydrides.  The  first  of  these,  catechu-tannic  acid, 
C38H34Oi5,  is  a  natural  constituent  of  catechu.  This  compound, 
and  the  dianhydride  C38H32OU,  and  the  trianhydride  C38H30O13, 
precipitate  gelatine,  and  have  a  resemblance  to  the  true  tannins. 
Further  heating  gives  rise  to  the  production  of  a  fourth  anhydride, 
catechuretin,  C38H28O12,  a  compound  insoluble  in  water. 

Catechin  reacts  with  two  molecules  of  diazobenzene  chloride, 
producing  a  catechinazobenzene. 

On  oxidation  with  potassium  bichromate,  catechin  yields 
japonic  acid,  a  reddish- brown  compound,  the  chromium  or  copper 


DYESTUFFS  OF  UNKNOWN  CONSTITUTION.  271 

lake  of  which  is  probably   formed  in  the  ordinary  methods  o£ 
dyeing  with  catechu. 

Catechu-tannic  Acid. — This  body,  also  known  as  catechin-red, 
is  obtained  by  extracting  catechu  with  cold  water,  or  by  heating 
catechin  with  water  to  110°.  It  precipitates  gelatine  but  not 
tartar-emetic,  and  gives  a  green  coloration  with  ferric  acetate. 

It  yields  a  reddish-brown  compound  on  oxidation  with  potas- 
sium bichromate,  probably  identical  with  the  japonic  acid  formed 
on  oxidation  of  catechin. 

Catechu  is  principally  used  in  cotton-dyeing.  It  gives  yel- 
lowish shades  on  goods  mordanted  with  aluminium  or  tin  salts ; 
but  its  main  application  is  for  the  production  of  brown  shades, 
which  are  very  fast.  The  goods  are  steeped  in  a  solution  of 
catechu  and  passed  through  a  bath  of  potassium  bichromate,  to 
which  copper  sulphate  is  sometimes  added.  The  brown  may 
also  be  developed  by  airing  or  ageing.  In  calico-printing,  catechu 
may  be  fixed  by  one  of  the  methods  used  for  aniline  black.  A 
mixture  of  catechu,  potassium  chlorate,  and  sal-ammoniac  is 
printed,  and  the  colour  developed  by  steaming. 

Cachou  de  Laval  [97]. 

The  above  dyestuff,  also  known  as  Fast  Grey,  is  a  commercial 
product  prepared  by  melting  various  organic  substances  (sawdust, 
bran,  &c.)  with  sodium  sulphide. 

These  products,  discovered  by  Croissant  and  Bretonniere,  contain 
peculiar  weak  acid  dyestuffs,  which  contain  sulphur. 

Cachou  de  Laval  dyes  unmordanted  cotton  from  an  alkaline  bath, 
producing  brownish  shades,  which  are  capable  of  modification  by 
passage  through  baths  of  various  metallic  salts  (copper  and  iron, 
chromium  salts).  In  spite  of  its  very  unpleasant  smell,  it  has  an 
extensive  application  in  cotton-dyeing. 

The  shades  are  very  fast  to  soap.  Like  canarin  and  the  direct 
dyeing  tetrazo-colours,  Cachou  de  Laval  is  capable  of  fixing  basic 
dyestuffs,  and  the  shades  can  thus  be  topped  at  will. 

By  fusing  sodium  acetate  with  sulphur,  E.  Kopp  obtained  a  sub- 
stance closely  resembling  Cachou  de  Laval  in  its  properties. 


REFERENCES. 


The  references  are  divided  into  the  following  sections  : — 

1.  INTRODUCTION. 

2.  NlTRO-COMPOUNDS. 

3.  AZO-COMPOUNDS. 

4.  OXYQUINONES  AND  QuiNONEOXIMES. 

5.  KETONEIMIDES  AND  HYDRAZIDES. 

6.  TBIPHENYLMETHANE  DYESTUFFS. 

7.  QuiNONEIMIDE  AND  AziNE  DYESTUFFS. 

8.  ANILINE  BLACK,  INDULINES  AND  NIGROSINES. 

9.  QuiNOLINE  AND  ACRIDINE  DYESTUFFS. 

10.  INDIGO  DYESTUFFS. 

11.  EUXANTHIC  ACID,  GALLOFLAVINE,  CANARINE,  AND  MUREXIDE. 

12.  DYESTUFFS  OF  UNKNOWN  CONSTITUTION. 


ABBREVIATIONS. 

Ber.  =  Berichte  der  deutschen  chemischen  Gesellschaft  zu  Berlin. 
Annal.  =  Annalen  d.  Chemie  und  Pharmazie  (now  Liebig's  Annalen). 
Journ.  f.  pr.  Chem.  =  Journal  fur  practische  Chemie. 
Jahresb.  =  Jahresbericht  iiber  die  Fortschritte  d.  Chemie  (Giessen :  Kicker, 

publisher). 
Friedl.  =  Dr.  P.  Friedlander : '  Fortschritte  der  Theerfarbenfabrication,'  1877- 

1887  and  1887-1890  (Berlin :  Julius  Springer,  publisher,   1888  and 

1891). 

INTRODUCTION. 

[1]  Runge,  Poggendorffs  Annal.  xxxi.  pp.  65  &  512 ;  Reichenbach,  Schweiger's 

Journal  f.  Ch.  Ixviii.  p.  1. 
[2]  Natanson,  Annal.  xcviii.  p.  297. 
[8]  Hofmann,  Jahresb.  1858,  p.  351. 
[4]  Renard  freres   et    Franc,  Brev.  d'invent.  of    8th  April,  1859,  and  five 

additional  patents. 

[5]  Gerber-Keller,  Brev.  d'invent.  of  29th  October,  1859. 
[6]  Medlock,  Brit,  patent  of  18th  January,  1860 ;  Nicholson,  Brit,  patent  of 

26th  January,  I860. 

T 


274  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

[7]  Girard  et  de  Laire,  Brev.  d'invent.  of  26th  May,  1860. 

[8]  Brev.  d'invent.  of  10th  December,  1861. 

[9]  Kolbe  and  Schmitt,  Annal.  cxix.  p.  169. 

[10]  Nicholson,  Monit.  scientif.  vii.  p.  5 ;  Brev.  d'invent.  of  10th  July,  1862. 
[11]  Monnet  et  Dury,  Brev.  d'invent.  of  30th  May,  18U2. 
[12]  Wanklyn,  Brit,  patent,  November  1862. 
[13]  A.  W.  Hofrnann,  Compt.  rend.  liv.  p.   428,  Ivi.  pp.  945  &  1033,  Ivii. 

p.  1131 ;  Jahresb.  1862,  p.  428 ;  Zeitsch.  f.  Ch.  1863,  p.  393. 
[14]  Usebe,  Brev.  d'invent.  of  28th  October,  1862. 
[15]  Lightfoot,  Brit,  patent,  17th  January,  1863;  Brev.  d'invent.  28th  January, 

1863. 

[16]  Martius  and  Griess,  Zeitsch.  f.  Ch.  ix.  p.  132. 
[17]  Caro  and  Griess,  Zeitsch.  f.  Ch.  x.  p.  278. 
[18]  Caro  and  Wanklyn,  Journ.  f.  pr.  Ch.  c.  p.  49. 
[19]  Keisser,  Brev.  d'invent.  18th  April,  1866. 
[20]  Girard,   de    Laire,  and  Chappotot,  Brev.   d'invent.  21st    March,   18C6, 

16th  March,  1867. 

[21]  Hofmann  and  Girard,  Ber.  ii.  p.  447. 
[22]  Rosenstiehl,  Bull,  de  1.  Soc.  industr.  de  Mulhouse,  1869. 
[23]  Ber.  ii.  p.  14. 

[24]  Hofmann  and  Geyger,  Ber.  v.  p.  526. 
[25]  Hofmann,  Ber.  vi.  p.  352. 
[26]  E.  and  O.  Fischer,  Ann.  cxciv.  p.  274. 
[27]  Germ,  patent  of  15th  December,  1877,  No.  1886. 
[28]  Ber.  ix.  p.  1035. 
[29]  E.  and  0.  Fischer,  Ann.  ccvi.  p.  130. 
[80]  Doebner,  Ber.  xi.  p.  1236. 
[31]  Germ,  patent,  No.  11857,  of  19th   March,   1880  j    Brit,    patent,   1880, 

No.  1177. 
[32]  Witt  and  Koechlin,  Germ,  patents,  No.  15915  and  No.  1958  j  Brit,  patents, 

1881,  No.  1373  and  No.  5249. 

[33]  Caro  and  Kern,  Amer.  patents,  25th  December,  1883,  22nd  April,  8th  July, 
and  2nd  December,  1884. 


NITRO-COMPOUNDS. 

[1]  Laurent,  Annal.  xliii.  p.  219. 

[2]  Schmitt  and  Glutz,  Ber.  ii.  p.  52. 

[3]  Schunck,  Ann.  xxxix.  p.  6,  Ixv.  p.  234. 

[4]  Piccard,  Ber.  viii.  p.  685. 

[5]  Martius  and  Wichelhaus,  Ber.  ii.  p.  207. 

[6]  Martius,  Zeitschr.  f.  Ch.  1868,  p.  80. 

[7]  Darmstadter  and  Wichelhaus,  Annal.  clii.  p.  299. 

[8]  Germ,  patent,  No.  10785,  of  28th  December,  1879;  Friedl.  i.  p.  327. 

[9]  Lauterbach,  Ber.  xiv.  p.  2028. 


REFERENCES.  275 


[10]  Merz  and  Weith,  Ber.  xv.  p.  2714. 

[11]  Gnehm,  Ber.  ix.  p.  1245. 

[12]  Hlasiwetz,  Annal.  ex.  p.  289. 

[18]  Schering,  Germ,  patent,  No.  15117  and  No.  15889. 


AZO-COMPOUNDS. 

[1]  Liebermann,  Ber.  xvi.  p.  2858. 

[2]  Zinke,  Ber.  xviii.  p.  3132. 

[3]  Zinke  and  Bindewald,  Ber.  xvii.  p.  3026. 

[4]  Spiegel,  Ber.  xviii.  p.  1479. 

[5]  Griess  and  Martins,  Zeitschr.  f.  Ch.  1866,  p.  132. 

[6]  Kekute,  Zeitschr.  f.  Ch.  1866,  p.  688. 

[7]  Janowsky,  Ber.  xix.  p.  2157. 

[8]  Graessler,  Germ,  patent.  4186 ;  Friedl.  i.  p.  439. 

[9]  Griess,  Ber.  xv.  p.  2183. 
[10]  Griess,  Ber.  x.  p.  528. 
[11]  Witt,  Chemikerzeit.  1880,  No.  26. 
[12]  Witt,  Ber.  xii.  p.  259. 
[13]  Nietzki,  Ber.  x.  pp.  662,  1155. 
[14]  Noelting  and  Witt,  Ber.  xii.  p.  77. 
[15]  Nietzki,  Ber.  xiii.  p.  472. 
[16]  Noelting  and  Forel,  Ber.  xviii.  p.  2681. 
[17]  Hofmann,  Ber.  x.  p.  213. 
[18]  Witt,  Ber.  x.  p.  656. 
[19]  Mixter,  Ainer.  Chem.  Journ.  v.  p.  282. 
[20]  Nietzki,  Ber.  xvii.  p.  345. 

[21]  Lippmann  and  Fleissner,  Ber.  xv.  p.  2136,  xvi.  p.  1415. 
[22]  Noelting,  Ber.  xviii.  p.  1143. 
[23]  Annal.  Ixxv.  p.  74. 
[24]  Annal.  cxxxv.  p.  164. 

[25]  Caro  and  Griess,  Zeitschr.  f.  Ch.  1867,  p.  278. 
[26]  Buckney,  Ber.  xi.  p.  1453. 
[27]  A.  W.  Hofmann,  Ber.  x.  p.  28. 
[28]  Griess,  Annal.  cxxxvii.  p.  60. 
[29]  Weselsky  and  Benedikt,  Ber.  xii.  p.  228. 
[30]  Perkin  and  Church,  Annal.  cxxix.  p.  108. 
[31]  Griess,  Annal.  cliv.  p.  211. 
[32]  KekulS  and  Hidegh,  Ber.  iii.  p.  234. 
[33]  Kimmich,  Ber.  viii.  p.  1026. 
[34]  Wallach  and  Kiepenheuer,  Ber.  xiv.  p.  2617. 
[35]  Baeyer  and  Jaeger,  Ber.  viii.  p.  148, 
[36]  Griess,  Ber.  xi.  p.  2192. 
[37]  Witt,  Ber.  v.  p.  2196. 
[38]  Jaeger,  B  er.  viii,  p.  1499. 

T2 


276  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

[39]  Liebermann  and  Kostanecki,  Ber.  xviii.  pp.  130  &  882. 

[40]  Wallach  and  Schutze,  Ber.  xv.  p.  3020. 

[41]  Mazzara,  Gaz.  chim.  It.  ix.  p.  424. 

[42]  Noel  ting  and  Kohn,  Ber.  xvii.  p.  351. 

[43]  Nietzki,  Ber.  xvii.  pp.  344  &  1350. 

[44]  Griess,  Ber.  xvii.  p.  608. 

[45]  Meister,  Lucius,  and  Briining,  Germ,  patent,  No.   3229,  of  24th  April, 

1878 ;  Brit,  patent,  1878,  No.  1715,  Friedl.  p.  377. 
[46]  Wallach,  Ber.  xv.  p.  2825. 
[47]  Germ,  patent,  No.  5411,  of  12th  March,  1878;  Brit,  patent,  1878,  No.  786; 

Friedl.  p.  358. 

[48]  Brit,  patent,  1881,  No.  2030  ;  Friedl.  p.  373. 
[49]  Griess,  Ber.  xiv.  p.  2032. 
[50]  Griess,  Ber.  x.  p.  527. 
[51]  Brit,  patent,  1880,  No.  4091. 
[52]  Stebbins,  Ber.  xiii.  p.  716. 
[53]  Frankland,  Journ.  of  Ch.  Soc.  xxxvii.  p.  747. 
[54]  Brit,  patent,  1881,  No.  1767 ;  FriedL  i.  p.  324. 
[55]  Germ,  patent,  No.  22707,  of  9th  September,  1882  j  Friedl.  p.  539. 
[56]  Griess,  Ber.  ix.  p.  627. 
[57]  Griess,  Ber.  xvi.  p.  2028. 

[58]  Germ,  patent,  No.  22714,  of  8th  November,  1882;  Friedl.  i.  p.  453. 
[59]  Caro  and  Schraube,  Ber.  x.  p.  2230. 
[60]  Nietzki,  Ber.  xiii.  p.  1838. 

[61]  Brit,  patent,  1881,  Nos.  1225,  2030 ;  Friedl.  p.  364. 
[62]  Journ.  of  the  Chem.  Soc.,  November  1883,  March  1884. 
[63]  Witt,  Brit,  patent,  1883,  No.  2237;  Friedl.  i.  p.  391. 
[64]  Germ,  patent,  No.  28753,  of  27th  February,  1884;  Friedl.  i.  p.  470. 
[65]  Paul,  Germ,  patent,  No.  28820,  of  13th  December,  1883 ;  Friedl.  p.  447. 
[66]  Brit,  patents,  1884,  Nos.  9162,  9606;  Friedl.  i.  p.  465. 
[67]  Brit,  patent,  1883,  No.  5767  ;  Friedl.  i.  p.  552.      . 
[68]  Oassella,  Brit,  patent,  1885,  No.  9214  ;  Friedl.  i.  p.  451. 
[69]  Farbenfabr.  Bayer   and  Co.,  Brit,  patent,  1885,  No.   3803;   Friedl.  i. 

p.  473. 

[70]  Farbenfabr.  Bayer,  Brit,  patent,  1885,  No.  14424 ;  Friedl.  i.  pp.  488-491. 
[71]  Schultz,  Ber.  xvii.  p.  463. 

[72]  Roussin  and  Poirrier,  Brit,  patent,  1878,  No.  4490  ;  Friedl.  i.  p.  531. 
[73]  Meister,  Lucius,  and  Briining,  Brit,  patent,  1878,  No.  1715. 
[74]  Griess,  Ber.  xiii.  p.  1956. 
[75]  Glaus  and  Oehler,  Ber.  xv.  p.  312. 
[76]  Baeyer  and  Duisberg,  Bsr.  xx.  p.  1426. 
[77]  Weinberg,  Ber.  xx.  pp.  2906  &  3353. 

[78]  Germ,  patent,  No.  38735,  of  29th  January,  1886  ;  Friedl.  i.  p.  510. 
[79]  Bender  and  Schultz,  Ber.  xix.  p.  3237. 
[80]  A.  G.  Green,  Journ.  of  Chem.  Ind.  1888,  p.  108;  Ber.  xxii.  p.  968;  Dahl 


REFERENCES.  277 

and  Co.,  Germ,  patent,  No.    47012,  of  8th  June,  1888;    Pfitzinger, 
Gattermann,  and  Jakobsen,  Ber.  xxii.  pp.  330,  422, 580, 1063  ;  (Erica)  : 
Engl.  patent,  1888,  No.  17333  ;  K.  Anschiitz  and  G.  Sehultz,  Ber.  xxii. 
p.  583. 
[81]  Engl.  patent,  1888,  No.  6319. 

OXYQU1NONES  AND  QUINONEOXIMES. 

[1]  Rochleder,  Annal.  Ixxx.  p.  324. 

[2]  Schunck,  Annal.  Ixvi.  p.  176 ;  Jahresb.  1855,  p.  666. 

[3]  Graebe  and  Liebermann,  Ann.  Suppl.  vii.  p.  300  j  Ber.  ii.  pp.  14,  332,  505, 
iii.  p.  359. 

[4]  Baeyer  and  Caro,  Ber.  vii.  p.  972. 

[5]  Schunck,  Jahresb.  1874,  p.  446. 

[6]  Schutzenberger,  '  Farbstoffe  '  (Berlin,  1870),  ii.  p.  114. 

[7]  Baeyer,  Ber.  ix.  p.  1232. 

[8]  Diehl,  Ber.  xi.  p.  187. 

[9]  Perkin,  Jahresb.  1874,  p.  485. 
[10]  Stenhouse,  Anual.  cxxx.  p.  343. 
[11]  Perger,  Journal  f.  pr.  Ch.  xviii.  p.  184. 
[12]  Graebe  and  Liebermann,  Annal.  clx.  p.  144. 
[13]  Wiedemann,  Ber.  ix.  p.  856. 
[14]  Brit,  patent,  No.  1936,  of  25th  June,  1869. 
[15]  Perkin,  Brit,  patent,  No.  1948,  of  26th  June,  1869. 
[16]  Meister,  Lucius,  and  Briining,  Jahresb.  1873,  p.  1122. 
[17]  Perkin,  Ber.  ix.  p.  281. 

[18]  Rosenstiehl,  Bullet,  de  la  Soc.  chirn.  xxvi.  p.  63. 
[19]  Schunck  and  Homer,  Ber.  xii.  p.  584. 
[20]  Strecker,  Annal.  Ixxv.  p.  20. 
[21]  De  Lalande,  Jahresb.  1874,  p.  486. 
[22]  Vogel,  Ber.  ix.  p.  1641. 
[23]  Lepel,  Ber.  ix.  p.  1845 ;  x.  p.  159. 
[24]  Auerbach,  Jahresb.  1874,  p.  488. 
[25]  Perkin,  Jahresb.  1873,  p.  450. 

[26]  Schunck  and  Homer,  Ber.  ix.  p.  679,  x.  p.  1823,  xiii.  p.  42, 
[27]  Caro,  Ber.  ix.  p.  682. 

[28]  Prudhomme,  Bullet,  de  la  Soc.  indust.  de  Mulhouse,  xxviii.  p.  62. 
[29]  Graebe,  Annal.  cci.  p.  333. 
[80]  Journ.  of  the  Chem.  Soc.  xxxv.  p.  800. 
[31]  Brit,  patent,  1881,  No.  3603 ;  Friedl.  i.  p.  168. 
[32]  Fitz,  Ber.  viii.  p.  631. 
[83]  Kostanecki,  Ber.  xx.  p.  3133. 
[34]  Fuchs,  Ber.  viii.  pp.  625  &  1026. 
[35]  Liebermann  and  Kostanecki,  Ber.  xviii.  p.  2138. 
[36]  Jakobsen  and  Julius,  Ber.  xx.  p.  2588. 
[37]  Kostanecki,  Ber.  xx.  p.  3143. 


278  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

[38]  Hoffmann,  Ber.  xviii.  p.  46. 

[39]  Brit,  patent,  1884,  No.  2269  ;  Friedl.  i.  p.  335. 

[38  a]  Graebe,  Ber.  xxiii.  p.  3739  j  Rob.  E.  Schmidt,  Journ.  f.  pract.  Ch.  xliii. 

p.  237 ;  Gattermann,  Journ.  f.  pract.  Ch.  xliii.  p.  246 ;  Engl.  patent, 

1890,  NosT  8725,  12715,  17712, 18729. 
[39  «]  Engl.  patent,  1884,  No.  2269. 
[40]  R.  E.  Schmidt  and  Gattermann,  Journ.  f.  pract.  Ch.  xliv.  p.  103  j  Engl. 

patent,  1888,  Nos.  14353,  15121. 
[41]  Seuberlich,  Ber.  x.  p.  38. 
[42]  R.  E.  Schmidt,  Journ.  f.  pract.  Ch.  xliii.  p.  232. 

KETONEIMIDES  AND  HYDRAZIDES. 

[I]  Brit,  patents,  1884,  Nos.   5512,  5741 ;   Caro  and  Kern,  Arner.  patents, 

December  25th,  1883,  April  22nd,  July  8th,  December  2nd,  1884; 

Friedl.  i.  p.  99. 
[2]  Michler,  Ber.  ix.  p.  716. 

[3]  Brit,  patent,  1886,  No.  120022  ;  Friedl.  p.  94;  Ber.  xix.,  Ref.  p.  889. 
[4]  Fehrmann,  Ber.  xx.  p.  2844. 
[5]  Graebe,  Moniteur  scientif.  1887,  p.  600. 
[6]  Ziegler  and  Locher,  Ber.  xx.  p.  834. 
[7]  Graebe,  Ber.  xx.  p.  3260. 
[8]  Engl.  patent,  1885,  No.  9858. 

TRIPHENYLMETHANE  DYESTUFFS. 

[1]  Brit,  patents,  1884,  Nos.  5512, 5741 ;  Caro  and  Kern,  Amer.  patents,  Decem- 
ber 25th,  1883,  April  22nd,  July  8th,  December  2nd,  1884 ;  Friedl.  i. 
p.  99. 

[2]  Bottinger,  Ber.  xii.  p.  975. 

[8]  E.  &  0.  Fischer,  Ber.  xi.  p.  950,  xii.  pp.  796  &  2348. 
[4]  O.  Doebner,  Ber.  xi.  p.  1236. 
[5]  O.  Fischer,  Annal.  ccvi.  p.  130. 
[6]  Brit,  patent,  1878,  No.  728  ;  Friedl.  p.  40. 
[7]  0.  Fischer,  Ber.  xiv.  p.  2521. 
[8]  0.  Fischer  and  T.  Ziegler,  Ber.  xiii.  p.  672. 
[9]  Brit,  patent,  1878,  No.  4406;  Friedl.  p.  117. 
[10]  Brit,  patent,  1879,  No.  2509. 

[II]  Germ,  patent,  No.  4988,  June  8th,  1878. 
[12]  E.  &  O.  Fischer,  Annal.  cxciv.  p.  274. 
[13]  Dale  and  Schorlemmer,  Ber.  x.  p.  1016. 

[14]  Germ,  patent,  No.  16750,  February  8th,  1881 ;  Friedl.  i.  p.  57. 

[15]  Ph.  Greiff,  Germ,  patent,  No.  15120,  January  26th,  1881 ;  Friedl.  i.  p.  49. 

[16]  Rosenstiehl,  Annal.  de  Chim.  &  Phys.  (5)  viii.  p.  192. 

[17]  Germ,  patent,  No.  16710,  February  24th,  1881. 

[18]  Brit,  patent,  1881,  No.  1212;  Friedl.  i.  p.  54. 

[19]  A.  W.  Hofmann,  Ber.  vi.  p.  352. 


REFERENCES.  279 

[20]  Greiff,  Brit,  patents,  1879,  Nos.  2515,  4828. 

[21]  Brunner  and  Brandenburg,  Ber.  x.  p.  1845,  xi.  p.  697. 

[22]  O.  Fischer  and  Koerner,  Ber.  xvii.  p.  98. 

[23]  Fischer  and  Germaner,  Ber.  xvi.  p.  706. 

[24]  E.  Fischer,  Ber.  xii.  p.  798. 

[25]  0.  Fischer  and  Koerner,  Ber.  xvi.  p.  2904. 

[26]  A.  W.  Hofmann,  Ber.  xviii.  p.  767. 

[27]  Lange,  Ber.  xviii.  p.  1918. 

[28]  Hofmann,  Compt.  rend.  liv.  p.  428,  Ivi.  pp.  1033  &  945,  Ivii.  p.  1131 ; 

Jahresb.  1862,  p.  347. 
[29]  Victor  Meyer,  Ber.  xiii.  p.  2343. 
[30]  Brit,  patents,  1877,  No.  3731  ;  1879,  No.  2828. 
[31]  Caro  and  Graebe,  Annal.  clxxix.  p.  203. 
[32]  Hofmann  and  Girard,  Ber.  ii.  p.  447. 
[33]  Hofmann,  Ber.  vi.  p.  263. 
[34]  Beckerhinn,  Jahresb.  1870,  p.  768. 
[35]  Schiitzenberger,  '  Matieres  color.,'  Paris,  1867,  i.  p.  506. 
[36]  Girard,  de  Laire,  and  Chappotot,  Zeitschr.  f.  Ch.  1867,  p.  236. 
[37]  Girard  and  de  Laire,  Jahresb.  1862,  p.  696. 
[38]  Hofmann,  Jahresb.  1863,  p.  417. 
[39]  Hofmann,  N.  Handworterbuch  d.  Ch.  i.  p.  626. 
[40]  Bulk,  Ber.  v.  p.  417. 

[41]  E.  Kopp,  Kiinstl.  Farbstoffe,  pp.  319  &  320. 
[42]  Usebe,  Journ.  f .  pr.  Ch.  xcii.  p.  337 ;  Lauth,  Bullet,  de  la  Soc.  Chim.  1861, 

p.  78 ;  French  patent,  June  26th,  1861. 
[43]  Hofmann,  Ber.  iii.  p.  761. 
[44]  Kolbe  and  Schmitt,  Annal.  cxix.  p.  169. 
[45]  Nencki  and  Schmitt,  Journ.  f.  pr.  Ch.  (2)  xxiii.  p.  549. 
[46]  Graebe  and  Caro,  Ber.  xi.  p.  1350. 
[47]  Liebermann  and  Schwarzer,  Ber.  ix.  p.  800. 
[48]  Dale  and  Schorlemmer,  Annal.  clxvi.  p.  281,  cxcvi.  p.  77. 
[49]  Zulkowsky,  Annal.  cxciv.  p.  119,  ccii.  p.  194 ;  Ber.  x.  p.  1201. 
[50]  Caro  and  Wanklyn,  Journ.  f.  pr.  Ch.  c.  p.  49. 
[51]  Runge,  Poggendorffs  Annal.  xxxi.  pp.  65  &  612. 
[52]  Persoz  fils,  Pelouze,  Traite*  de  Chirnie. 
[53]  Guinon,  Mamas,  and  Bonnet,  Brev.  d'invent.  1862. 
[54]  Reichenbach,  Schweiger's  Journ.  f.  Ch.  Ixviii.  p.  1. 
[55]  Liebermann,  Ber.  ix.  p.  334. 
[56]  Hofmann,  Ber.  xi.  p.  1455,  xii.  pp.  1371  &  2216. 
[57]  Poebner,  Ber.  xii.  p.  1462,  xiii.  p.  610. 
[58]  Baeyer,  Ber.  iv.  p.  662. 
[59]  Claus  and  Andreae,  Ber.  x.  p.  1305. 
[60]  Gukassianz,  Ber.  xi.  p.  1179. 
[61]  Rosicki,  Ber.  xiii.  p.  208. 
[62]  Baeyer,  Annal.  ccii.  p.  68. 


280  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

[63]  Baeyer,  Annal.  clxxxiii.  p.  1. 

[64]  Hofmann,  Ber.  viii.  p.  62. 

[65]  Baeyer,  Ber.  iv.  pp.  457,  663. 

[66]  Buchka,  Annal.  ccix.  p.  261. 

[67]  Reichl,  Dingl.  Polyt.  Journ.  ccxxxv.  p.  232. 

[68]  A.  Kern,  Germ,  patent. 

[69]  Girard  and  de  Laire,  Jahresb.  1867,  p.  963. 

[70]  L.  Gattermann  and  Wichmann,  Ber.  xxii.  p.  227. 

[71]  W.  v.  Miller  and  Plochl,  Ber.  xxiv.  p.  1700. 

[72]  M.  Nathanson  and  P.  Miiller,  Ber.  xxii.  p.  1888. 

[73]  Engl.  patent,  1889,  No.  3333. 

[74]  Heumann  and  Rey,  Ber.  xxii.  p.  3001. 

[75]  M.   Ceresole,  Engl.  patents,  1887,  No.  15374,  1888,  No.   9600,   1889, 

No.  2635. 
[76]  Engl.  patent,  1889,  No.  13217. 

QUINONEIMIDE  AND  AZINE  DYESTUFFS. 

[1]  Nietzki,  Ber.  xvi.  p.  464. 

[2]  Bindschedler,  Ber.  xvi.  p.  865. 

[3]  Bindschedler,  Ber.  xiii.  p.  207. 

[4]  Witt,  Ber.  xii.  p.  931. 

[5]  Wurster  and  Sendtner,  Ber.  xii.  p.  1803  ;  Wurster,  Ber.  xii.  p.  2072. 

[6]  Wurster  and  Schobig,  Ber.  xii.  p.  1809. 

[7]  Koechlin  and  Witt,  Brit,  patents,  1881,  Nos.  1373,  5249 ;  Friedl.  i.  p.  283. 

[8]  Witt,  Journ.  of  Chem.  Ind.  1882. 

[9]  Cassella,  Germ,  addit.  patent,  No.  15915  ;  Friedl.  p.  285. 
[10]  Schmitt  and  Andressen,  Journ.  f.  pract.  Ch.  (2)  xxiv.  p.  435. 
[11]  Hirsch,  Ber.  xiii.  p.  1909. 
[12]  Mohlau,  Ber.  xvi.  p.  2845. 
[13]  Bernthsen,  Ber.  xvii.  p.  611. 
[14]  Lauth,  Ber.  ix.  p.  1035. 
[15]  Engl.  patent,  No.  3751. 
[16]  Bernthsen,  Ber.  xvi.  pp.  2903  &  1025. 
[17]  Mohlau,  Ber.  xvi.  p.  2728. 
[18]  Nietzki,  Ber.  xvii.  p.  223. 
[19]  Koch,  Ber.  xii.  p.  592. 
[20]  Engl.  patent,  1880,  No.  2906. 

[21]  Mulhauser,  Germ,  patent,  No.  23291,  3rd  January,  1883. 
[22]  0.  N.  Witt,  Ber.  xii.  p.  939. 
[23]  0.  N.  Witt,  Journ.  Soc.  Chem.  Ind.  1882. 
[24]  Hofmann  &  Geyger,  Ber.  v.  p.  526. 
[25]  Witt,  Ber.  xviii.  p.  1119. 
[26]  Private  communication. 
[27]  A.  W.  Hofmann,  Ber.  ii.  p.  374. 

[28]  Perkin,  Jahresb.  1859-1863;  and  Proc.  of  the  Royal  Soc.  XXXY.  p.  717. 
[29]  Meldola,  Ber.  xii.  p.  2065. 


REFERENCES.  281 

[30]  Liebermann,  Ber.  vii.  pp.  247  &  1098. 

[31]  Weselsky,  Annal.  clxii.  p.  273. 

[82]  H.  Koechiin,  Engl.  patent,  1881,  No.  4899 ;  Friedl.  i.  p.  269. 

[33]  Weselsky  and  Benedikt,  Wiener  Monatshefte,  i.  p.  886 ;  Ber.  xiv.  p.  530. 

[34]  Brunner  and  Kramer,  Ber.  xvii.  p.  1817. 

[35]  Bindschedler  and  Busch,  Eng.  patent  1881,  No.  939. 

[86]  Bernthsen,  Annal.  ccxxx.  pp.  73  &  211. 

[37]  Witt,  Ber.  xviii.  p.  1119. 

[38]  Witt,  Ber.  xix.  p.  411. 

F39]  Bernthsen,  Ber.  xix.  p.  2604 ;  Annal.  ccxxxvi.  p.  332. 

[40]  Witt,  Ber.  xix.  p.  2791. 

[41]  Nietzki,  Ber.  xix.  pp.  3017  &  3136. 

[42]  Witt,  Ber.  xix.  p.  3121. 

[43]  Nietzki,  Ber.  xix.  p.  3017. 

[44]  Julius,  Ber.  xix.  p.  1365. 

[45]  Witt,  Ber.  x.  p.  873. 

[46]  Wiener  Monatsh.,  July  1884. 

[47]  Eng.  patent,  1886,  No.  43  ;  Friedl.  i.  p.  254. 

[48]  R.  Nietzki,  Ber.  x.  p.  1157. 

[49]  Nietzki  and  Otto,  Ber.  xxi.  p.  1590. 

[50]  Nietzki  and  Otto,  Ber.  xxi.  p.  1598. 

[51]  Nietzki  and  Otto,  Ber.  xxi.  p.  1736. 

[52]  Witt,  Ber.  xxi.  p.  719. 

[53]  Eng.  patent,  1888,  No.  5852. 

[54]  Eng.  patent,  1886,  No.  14283. 

[55]  Eng.  patent,  1890,  No.  3098. 

[54 a]  R.  Nietzki,  A.  Dietze,  &Mackler,  Ber.  xxii.  p.  3030. 

[55  a]  Nietzki  and  Mackler,  Ber.  xxiii.  p.  720. 

[56]  Germ,  patent,  1886,  No.  40868. 

[57]  O.  Fischer  and  E.  Hepp,  Ber.  xxi.  p.  2620. 

[58]  Germ,  patent,  1888,  No.  49853. 


ANILINE  BLACK,  INDULINES  AND  NIGROSINES. 

[1]  Lauth,  Bullet,  d.  1.  Soc.  chim.  Dec.  1864. 

[2]  Castelhaz,  Deutsche  Industriez.  1874. 

[3]  Persoz,  Deutsche  Industriez.  1868. 

[4]  E.  Kopp,  Moniteur  scientif.  1861,  p.  79. 

[5]  Rich  Meyer,  Ber.  ix.  p.  141. 

[6]  Fritzsche,  Journ.  f.  pract.  Chem.  xxviii.  p.  202. 

[7]  Lightfoot,  Jahresb.  1872,  p.  1076. 

[8]  Witz,  Jahresber.  1877,  p.  1239. 

[9]  Nietzki,  Unpublished  observations. 
[10]  Coquillon,  Compt.  rend.  Ixxxi.  p.  404. 
[11]  Nietzki,  Ber.  ix.  p.  616. 
[12]  B.  Kayser,  Verh.  d.  Kgl.  Gewerbemuseums  z.  Niirnberg,  1877. 


282  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

[13]  Witt,  and  Thomas,  Ber.  xvi.  p.  1102. 

[14]  Calvert,  Lowe,  Clifft,  Eng.  patent,  June  llth,  1860. 

[15]  Goppelsroeder,  Jahresber.  1876,  p.  702. 

[16]  Caro,  Private  communication. 

[17]  Nietzki,  Ber.  xvii.  p.  223. 

[18]  Nietzki,  Ber.  ix.  p.  1168. 

[19]  Lauth,  Bull.  d.  1.  Soc.  chim.  Dec.  1864. 

[20]  Cordelot,  Monit.  scientif.  vi.  p.  569. 

[21]  Caro  and  Dale,  Dingl.  Journ.  clix.  p.  46-5. 

[22]  Martius  and  Griess,  Zeitschr.  f,  Chem.  1866,  p.  136. 

[23]  Hof  inann  and  Geyger,  Ber.  v.  p.  472. 

[24]  v.  Dechend  and  Wichelhaus,  Ber.  viii.  p.  1609. 

[25]  Stadeler,  Dingl.  Journ.  clxxvii.  p.  395. 

[26]  Witt,  Ber.  xvii.  p.  74. 

[27]  Witt  and  Thomas,  Chem.  Soc.  Journ.  1883,  p.  112. 

[28]  Kimmich,  Ber.  viii.  p.  1028. 

[29]  Caro,  Neues  Haudworterb.  d.  Chem.,  Art.  Indulin. 

[30]  Coupier,  French  patent,  No.  77854. 

[31]  Justus  Wolff,  Chem.  News,  xl.  p.  4. 

[32]  Kruis,  Jahresb.  1874,  p.  1217. 

[33]  Liechti  and  Suida,  Wagner's  Jahresber.  1884,  p.  546. 

[34]  Nietzki,  Ber.  xi.  p.  1094;    Verb.  d.  Vereins   z.   Bef.   d.    Gewerbefleisses 

Berlin,  1877. 

[35]  Fischer  and  Hepp,  Annal.  cclvi.  p.  263,  cclxii.  p.  237,  cclxvi.  p.  249. 
[36]  Meister,  Lucius,  and  Briining,  Eugl.  patent,  1888,  No.  16325 ;  Friedl.  ii. 

p.  195. 

[37]  0.  Fischer  and  E.  Hepp,  Ber.  xxi.  p.  2617 ;  Ber.  xxiii.  p.  838. 
[38]  Chemikerzeitung,  1891. 
[39]  Dahl  and  Co.,  Germ,  patent  No.  36899,  March  llth,  1886,  Nos.  39763, 

45803, 43008;  Farbwerke,  Meister,  Lucius,  and  Briining,  Germ,  patent, 

No.  50819. 

[40]  Oehler,  Germ,  patent,  No.  533357. 
[41]  Meister,  Lucius,  and  Bruning,  Germ,  patent,  No.  34515. 
[42]  O.  Fischer  and  Hepp,  Ber.  xxi.  p.  2621. 
[43]  C.  Schraube,  Eng.  patent,  No.  15259,  October  23rd,  1888,  and  No.  6875  of 

1890. 

[44]  Annal.  cclvi.  p.  240. 
[45]  0.  Fischer  and  E.  ftepp,  Ber.  xxiii.  pp.  2789-2793. 


QUINOLINE  AND  ACRIDINE  DYESTUFFS. 

[1]  Jacobsen  and  Reimer,  Ber.  xvi.  p.  1082. 

[2]  Hofmann,  Jahresb.  1862,  p.  351. 

[3]  Nadler  and  Merz,  Jahresb.  1867,  p.  512. 

[4]  Hoogewerff  and  van  Dorp,  Ber.  xvii.  Kef.  p.  48. 

[6]  Williams,  Chem.  News,  ii.  p.  219. 


REFERENCES.  283 

[6]  Jacobsen,  Germ,  patents  23962,  December  16th,  1882 ;  23188,  November 
4th,  1882;  Friedl.  i.  p.  161. 

[7]  Jacobsen  and  Reimer,  Ber.  xvi.  p.  2604. 

[8]  Fischer  and  Rudolf,  Ber.  xv.  p.  1500;  Fischer  and  Besthorn,  Ber.  xvi. 
p.  68. 

[9]  Fischer  and  Timber,  Ber.  xvii.  p.  2925. 
[10]  Fischer  and  Bedall,  Ber.  xv.  p.  684. 
[11]  Hofmann,  Jahresber.  1862,  p.  346:  Ber.  ii.  p.  379. 
[12]  Fischer  and  Koerner,  Ber.  xvii.  p.  203. 
[13]  Anschiitz,  Ber.  xvii.  p.  434. 
[14]  Renouf,  Ber.  xvi.  p.  1304. 
[15]  A.  W.  Hofmann,  Ber.  xx.  p.  5. 
[16]  Hlasiwetz  and  Gilm,  Annal.  Supl.  ii.  p.  191. 
[17]  Weidel,  Ber.  xii.  p.  410. 
[18]  Fiirth,  Wiener  Monatshefte,  ii.  p.  416. 
[19]  Boedecker,  Annal.  xxiv.  p.  228. 
[20]  Biichner,  Annal.  Ixix.  p.  40. 
[21]  Oehler,  Eng.  pat.  1888,  No.  9614. 

[22]  Leonhardt  and  Co.,  Eng.  patent,  No.  17971,  1889 ;  and  English  patent, 
1890,  No.  8243. 


INDIGO  DYESTUFFS. 

[1]  Baeyer,  Annal.  Suppl.  vii.  p.  56 ;  Baeyer,  Ber.  xv.  p.  785. 

[2]  Nencki,  Ber.  vii.  p.  1593,  viii.  p.  336. 

[3]  Engler  and  Janeke,  Ber.  ix.  p.  1411. 

[4]  Nencki,  Journ.  f.  pract.  Chem.  [2]  xvii.  p.  98. 

[5]  Baeyer  and  Emmerling,  Ber.  ii.  p.  680. 

[6]  Baeyer  and  Caro,  Ber.  x.  pp.  692  &  1262. 

[7]  Morgan,  Jahresb.  1877,  p.  788. 

[8]  Widmann,  Ber.  xv.  p.  2547. 

[9]  Lipp,  Ber.  xvii.  p.  1072. 
[10]  Hofmann  and  Konigs,  Ber.  xvi.  p.  738. 
[11]  Forrer,  Ber.  xvii.  p.  984. 

[12]  Baumann  and  Tiemann,  Ber.  xii.  p.  1192,  xiii.  p.  415. 
[13]  Bayer,  Ber.  xiv.  p.  1741. 
[14]  Bayer  and  Knop,  Annal.  cxi.  p.  29. 
[15]  Suida,  Ber.  xi.  p.  584. 

[16]  Erdmann,  Journ.  f.  pract.  Chem.  xxiv.  p.  11 ;  Laurent,  ibid.  xxv.  p.  434. 
[17]  Baeyer,  Ber.  xi.  p.  1228. 

[18]  Friedlander  and  Ostermaier,  Ber.  xiv.  p.  1921. 
[19]  Baeyer,  Ber.  xiii.  p.  2259. 
[20]  Friedlander  and  Wleiigel,  Ber.  xvi.  p.  2227. 

[21]  E.  v.  Meyer,  Ber.  xviii.  Ref.  p.  274;  Journ.  f.  pr.  Ch.  (2)  xxx.  p.  467. 
[22]  Baeyer,  Ber.  xii.  p.  456. 
[23]  Baeyer  and  Oekonomides,  Ber.  xv.  p.  2093. 


284  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

[24]  Baeyer  and  Comstock,  Ber.  xvi.  p.  1704. 

[25]  Gabriel,  Ber.  xvi.  p.  518. 

[26]  Claisen  and  Sliadwell,  Ber.  xii.  p.  350. 

[27]  Baeyer,  Ber.  xv.  pp.  50  &  746. 

[28]  Baeyer,  Ber.  xv.  p.  775. 

[29]  Schunck,  Phil.  Magazine  (4)  x.  p.  73,  xv.  pp.  29,  117,  183;    Jahresb. 

1855,  p.  660,  1858,  p.  465. 
[30]  Fritsche,  Annal.  xliv.  p.  290. 
[31]  Sommaruga,  Annal.  cxcv.  p.  305. 
[32]  Schwarz,  Jahresb.  1863,  p.  557. 
[33]  Baeyer,  Ber.  xii.  p.  1315. 

[34]  Crum,  Berzelius  Jahresb.  iv.  p.  189 ;  Berzelius,  Berz.  Jahresb.  iv.  p.  190. 
[35]  Dumas,  Annal.  xlviii.  p.  257. 
[36]  Loew,  Ber.  xviii.  p.  950. 

[37]  Germ,  patent,  No.  32238  of  March  28th,  1884;  Friedl.  i.  p.  145. 
[38]  Baeyer  and  Emmerling,  Ber.  iii.  p.  514. 
[89]  Engler  and  Emmerling,  Ber.  iii.  p.  885. 
[40]  Nencki,  Ber.  viii.  p.  727,  vii.  p.  1593,  ix.  p.  299. 
[41]  A.  Baeyer,  Eng.  patent,  1880,  No.  1177,  and  Germ,  patent,  No.  11857, 

March  19th,  1880;  Friedl.  i.  p.  127. 

[42]  Glaser,  Annal.  cxliii.  p.  325,  cxlvii.  p.  78,  cliv.  p.  137. 
[43]  Germ,  patent,  No.  19266,  December  23rd,  1881 ;   Friedl.  i.  p.  136 ;  Eng. 

patent  1882,  No.  1266 ;  Friedl.  i.  p.  140. 
[44]  Baeyer  and  Drewsen,  Ber.  xv.  p.  2856. 
[45]  Baeyer  and  Drewsen,  Ber.  xvi.  p.  2205. 
[46]  Eng.  patent,  1882,  No.  1453 ;  Friedl.  i.  p.  141. 
[47]  Claisen,  Ber.  xiv.  pp.  350,  2460,  2468. 
[48]  Meister,  Lucius,  and  Briining,  Eng.  patent,  1882,  No.  3216;   Friedl.  i. 

p.  142. 

[49]  Germ,  patent,  No.  21592,  12th  August,  1882 ;  Friedl.  i.  p.  138. 
[50]  Gevekoht,  Annal.  ccxxi.  p.  330  ;  Germ,  patent,  No.  23785, 13th  January, 

1883;  Friedl.  i.  p.  139. 
[51]  Baeyer  and  Bloem,  Ber.  xvii.  p.  963. 
[62]  P.  Meyer,  Ber.  xvi.  p.  2261,  Germ,  patent,  No.  25136,  2nd  March,  1883  ; 

No.  27979,  22nd  December,  1883;  Friedl.  i.  pp.  148  &  149. 
[53]  Kekule-,  Ber.  ii.  p.  748. 
[54]  Baeyer,  Ber.  xvi.  p.  769. 
[55]  Baeyer,  Ber.  xvi.  p.  2188. 
[56]  Baeyer,  Ber.  xv.  p.  782. 
[57]  Compt.  rend.  xii.  p.  539. 
[58]  Baeyer  and  Lazarus,  Ber.  xviii.  p.  2637. 
[69]  Baeyer,  Ber.  xiii.  p.  2254. 
[60]  Forrer,  Ber.  xvii.  p.  976. 
[61]  Schunck,  Mem.  of  Manchester  Phil.  Soc.  (2)  xiv.  pp.  185-237 ;  Ber.  xii. 

p.  1220. 

[62]  Liubawin,  Journ.  d.  russ.  Chem.  Ges.  xiii.  p.  659. 
[63]  Schiitzenberger,  Jahresb.  1877,  p.  611 ;  Giraud's  Jahresb.  1880,  p.  586. 
[64]  E.  Fischer,  Ber.  xix.  p.  1563,  xvii.  p.  559. 


REFERENCES.  285 


EUXANTHIC    ACID,    GALLOFLAVINE,    CANARINE, 
AND    MUREXIDE. 

[1]  Stenhouse,  Annal.  li.  p.  423. 

[2]  Erdmann,  Journ.  f.  pr.  Ch.  xxxiii.  p.  190. 

[3]  Baeyer,  Annal.  civ.  p.  257. 

[4]  Graebe  and  Ebrard,  Ber.  xv.  p.  1675. 

[5]  Schmidt,  Annal.  xciii.  p.  88. 

[6]  Spiegel,  Ber.  xv.  p.  1964. 

[7]  Graebe,  Ber.  xix.  p.  2607. 

[8]  v.  Kostanecki,  Ber.  xix.  p.  2918. 

[9]  Wichelhaus  and  Salzmann,  Ber.  x.  p.  1397. 
[10]  Graebe,  Ber.  xix.  p.  2607. 
[11]  Bonn  and  Graebe,  Ber.  xx.p.  2327. 

[12]  Germ,  patent,  No.  37934,  20th  April,  1886 ;  Friedl.  i.  p.  567. 
[13]  Prochoroff  and  Miller,  Dingl.  Journ.  ccliii.  p.  130. 
[14]  Markownikoff,  Journ.  d.  russ.  Chem.  Ges.  1884,  p.  380. 
[15]  Lindow,  ibid.  1884,  p.  271. 
[16]  Liebig,  Poggend.  Annal.  xv.  p.  546. 
[17]  Prout,  Annal.  d.  Chim.  &  Phys.  xi.  p.  48. 
[18]  Liebig  and  Wohler,  Annal.  xxvi.  p.  319. 
[19]  Fritsche,  Annal.  xxxii.  p.  316. 
[20]  Beilstein,  Annal.  cvii.  p.  176. 
[21]  Graebe,  Annal.  ccliv.  p.  265. 
[22]  R.  Bohn,  Engl.  patent,  No.  8373,  20th  May,  1889  ;  Engl.  patent,  No.  9427, 

28th  June,  1859  ;  Graebe  and  Eichengriin,  Ber.  xxiv.  p.  967. 
[23]  Nencki  and  Siebert,  Journ.  f.  pr.  Ch.  xxiii.  pp.  147  &  538;  Badische 
Aniline  and  Sodafabrik.,  Engl.  patent,  1889,  No.  9429. 


DYESTUFFS  OF  UNKNOWN  CONSTITUTION. 

[1]  Chevreul,  Annal.  d.  Chim.  et  Phys.  (2)  Ixxxii.  pp.  53-126 ;  Le9ons  de 
Chimie  a  la  teinture,  ii. ;  Journ.  de  Chimie  Medicale,  vi.  p.  157. 

[2]  Erdmann,  Annal.  xliv.  p.  292. 

[3]  Hesse,  Annal.  cix.  p.  332. 

[4]  Rammelsberg,  Jahresb.  1857,  p.  490. 

[5]  Reim,  Ber.  iv.  p.  329. 

[6]  Buchka,  Ber.  xvii.  p.  683. 

[7]  Halberstadt  and  Reis,  Ber.  xiv.  p.  611. 
.  [8]  Hummel  and  Perkin,  Ber.  xv.  p.  2344. 

[9]  E.  Kopp,  Ber.  vi.  p.  447. 
[10]  Bolley,  Journ.  f.  j>r.  Ch.  cliii.  p.  351. 
[11]  Liebermann  and  Burg,  Ber.  ix.  p.  1885. 
[12]  Benedict,  Annal.  clxxviii.  p.  100. 


286  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

[13]  Dralle,  Ber.  xyii.  p.  372. 

[14]  Buchka  and  Erck,  Ber.  xviii.  p.  1138. 

[15]  Wiedemann,  Ber.  xvii.  p.  194. 

[16]  Loewe,  Fresenius  Zeitscbr.  xiv.  p.  119 

[17]  Wagner,  Journ.  f.  pr.  Oh.  li.  p.  482. 

[18]  Hlasiwetz  and  Pfaundler,  Annal.  cxxvii.  p.  353. 

[19]  Benedict,  Ber.  viii.  p.  606. 

[20]  Koch,  Ber.  v.  p.  285. 

[21]  Hlasiwetz,  Annal.  cxii.  p.  109. 

[22]  Zwenger  and  Dronke,  Annal.  Suppl.  i.  p.  267. 

[23]  Bolley,  Annal.  xxxvii.  p.  101. 

[24]  Rigaud,  Annal.  xc.  p.  283. 

[25]  Liebermann  and  Hamburger,  Ber.  xii.  p.  1179. 

[26]  Rochleder,  Jahresb.  1859,  p.  523. 

[27]  Bolley,  Anual.  cxv.  p.  54. 

[28]  Hlasiwetz  and  Pfaundler,  Jahresb.  1864,  p.  560 ;  Stein,  Jahresb.  1862, 

p.  500. 

[29]  Stein,  Journ.  f.  pr.  Ch.  Iviii.  p.  309. 
[30]  Borntrager,  Annal.  Ixxxii.  p.  197. 
[31]  Hlasiwetz,  Annal.  xcvi.  p.  123. 

[32]  Kane,  Berz.  Jahresb.  xxiv.  p.  505 ;  Gelatly,  Jahresb.  1858,  p.  473. 
[33]  Schiitzenberger,  Jahresb.  1868,  p.  774. 
[34]  Liebermann  and  Hormann,  Annal.  cxcvi.  p.  307. 
[35]  Smorawsky,  Ber.  xii.  p.  1595. 

[36]  Moldenhauer,  Annal.  c.  p.  180  ;  Journ.  f.  pr.  Ch.  Ixx.  p.  428. 
[37]  Rochleder,  Zeitschr.  f.  Chem.  1866,  p.  602. 
[38]  Schutzenberger  and    Paraf,   Jahresb.  1861,  p.  707;   Bullet,  de  la  Soc. 

Chimique,  1861,  p.  18. 
[39]  Schutzenberger  andBerteche,  Bullet,  d.  Mulhouse,  xxxv.  p.  455  ;  Jahresb. 

1868,  p.  776. 

[40]  Stenhouse,  Annal.  li.  p.  423. 
[41]  Erdmann,  Journ.  f.  pr.  Ch.  xxxiii.  p.  190. 
[42]  Baeyer,  Annal.  civ.  p.  257. 
[43]  Graebe  and  Ebrard,  Ber.  xv.  p.  1675. 
[44]  W.  Schmidt,  Annal.  xciv.  p.  88. 
[45]  Spiegel,  Ber.  xv.  p.  1964. 
[46]  Wichelhaus  and  Salzmann,  Ber.  x.  p.  1397. 
[47]  Graebe,  Ber.  xix.  p.  2607. 
[48]  Piccard,  Journ.  f.  pr.  Ch.  1861,  p.  709. 
[49]  Mylius,  Journ.  f.  pr.  Ch.  1864,  p.  546. 
r50]  Stein,  Jahresb.  1867,  p.  731. 
[51]  Etti,  Ber.  xi.  p.  864. 
[52]  Piccard,  Ber.  vi.  p.  884. 
[53]  Daube,  Ber.  iii.  p.  609. 
[54]  Iwanow-Gajewsky,  Ber.  iii.  p.  624, 


REFERENCES.  287 

[55]  Kachler,  Ber.  iii.  p.  713. 

[56]  Jackson,  Ber.  xiv.  p.  485. 

[57]  Wackenroder,  Berg.  Jahresb.  xii.  p.  277. 

[58]  Zeise,  Annal.  Ixii.  p.  202. 

[59]  Husemann,  Annal.  cxvii.  p.  200. 

[60]  Kane,  Annal.  xxxix.  p.  25. 

[61]  Robiquet,  Annal.  xv.  p.  292. 

[62]  Dumas,  Anual.  xxvii.  p.  147. 

[63]  Liebermann,  Ber.  vii.  p.  247,  viii.  p.  1649. 

[81  a]  Wartha,  Ber.  ix.  p.  217. 

[62  a]  Schlieper,  Annal.  Iviii.  p.  362. 

[63  a]  Malin,  Annal.  cxxxvi.  p.  117. 

[64]  Luynes,  Jahresb.  1864,  p.  551. 

[65]  Leo  Meyer,  Jahresb.  1847,  p.  784. 

[66]  Weyermann  and  Hafely,  Annal.  Ixxiv.  p.  22(3. 

[67]  Franchimont,  Ber.  xii.  p.  14. 

[68]  Pelletier,  Annal.  Iviii.  p.  27. 

[69]  Bolleyand  Wydler,  Annal.  Ixii.  p.  141. 

[70]  Carnelutti  and  Nasini,  Ber.  xiii.  p.  1514. 

[71]  Quadrat,  Jahresb.  1851,  p.  532. 

[72]  Weiss,  Zeitschr.  f.  Chemie,  1865,  p.  552. 

[73]  L.  Meyer  and  Kochleder,  Journ.  f.  pr.  Oh.  xxiv.  p.  1. 

[74]  K.  Kayser,  Ber.  xvii.  p.  2228. 

[75]  Cloez  and  Guignet,  Jahresb.  1872,  p.  1068. 

[76]  Kayser,  Ber.  xviii.  p.  3417. 

[77]  Schaller,  Jahresb.  1864,  p.  410  j  Zeitschr.  f.  Chem.  1865,  p.  140. 

[78]  Warren  De  La  Eue,  Annal.  Ixiv.  p.  1. 

[79]  Schiitzenberger,  Jahresb.  1858. 

[80]  Hlasiwetz  and  Grabowsky,  Annal.  cxli.  p.  329. 

[81]  Will  and  Leymann,  Ber.  xviii.  p.  3180. 

[82]  Liebermann  and  van  Dorp,  Annal.  clxiii.  p.  105. 

[83]  Liebermann,  Ber.  xviii.  p.  1975. 

[84]  Lacaze  Duthiers,  Wagner's  Jahresb.  1860,  p.  448. 

[85]  Schunck,  Ber.  xii.  p.  1359. 

[86]  Perrins,  Annal.,  Suppl.  ii.  p.  191. 

[87]  Fleitmann,  Annal.  lix.  p.  60. 

[88]  Hlasiwetz  u.  v.  Gilm,  Annal.,  Suppl.  ii.  p.  191. 

[89]  Weidel,  Ber.  xii.  p.  410. 

[90]  Fiirth,  Wiener  Monatshefte,  ii.  p.  416. 

[91]  Boedecker,  Annal.  xxiv.  p.  228. 

[92]  Biichner,  Annal.  Ixix.  p.  40. 

[92]  R.  Meyer,  Ber.  xii.  p.  1393. 

[93]  Liebermann  and  Roemer,  Ber.  xx.  p.  2428. 

[94]  J.  Schmid,  Ber.  xix.  p.  1734. 

[95]  R.  E.  Schmidt,  Ber.  xx.  p.  1285. 


288  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

[96]  Arnaud,  Compt.  rendus,  cii.  p.  1119. 
[97]  Witt,  Ber.  vii.  pp.  1530  &  1746. 
[98]  Bizio,  Ber.  vi.  p.  142. 
[99]  G.  Schultz,  Annal.  ccii. 
[100]  C.  Schall  and  Dralle,  Ber.  xxiii.  p.  1433. 

[105]  Liebermann  and  Tauchert,  Ber.  xiii.  p.  694 ;  see  also  Neubauer,  Annal. 
xcvi.  p.  337 ;  Kraut  and  Delden,  Annal.  cxxviii.  p.  285 ;  Etti,  Annal. 
clxxxvi.  p.  327  ;  Schiitzenberger  and  Rack,  Bullet,  d.  1.  Soc.  Chim.  iv. 
p.  5  ;  Hlasiwetz,  Annal.  cxxxiv.  p.  118. 
[106]  Etti,  Wiener  Monatshefte,  ii.  p.  547. 


APPENDIX, 


NITRO-COMPOUNDS. 

P.  25.  Naphthol  Yellow  S. 

The  G-naphtholtrisulphonic  acid  used  in  the  manufacture  of 
naphthol  yellow  S  has  the  constitutional  formula  : 


OH 


S03H 


S09H 


S03H 


The  free  acid  of  naphthol  yellow  S  is  constituted  according  to 
the  formula  : 

OH 


S03H 


AZO-DYES. 

P.  56.  Chromotropes. 

These  colouring-matters  are  prepared  by  action  of  diazo-com- 
pounds  on  the  chromotrope  acid  (see  p.  295).      The  commercial 

u 


290  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

brands  are  2  R,  2  B,  6  B,  8  B,  and  10  B.  They  dye  wool  from  an 
acid  bath ;  the  shades  vary  from  a  bright  scarlet  with  2  R  to  a 
reddish  violet  with  10  B,  but  are  not  fast  to  soap.  More  valuable 
results  are  obtained  when  the  chromotropes  are  applied  in  con- 
junction with  a  mordant.  Darker  and  faster  shades  are  obtained 
by  boiling  the  goods  dyed  with  these  dyestuffs  with  salts  of  copper, 
aluminium,  and  iron,  and  various  shades  of  black  are  produced  by 
action  of  potassium  bichromate.  It  has  been  found  advantageous 
to  use  the  mordant  after  dyeing,  the  operation  taking  place  in  the 
same  bath.  Chromotrope  8  B  gives  the  best  and  fastest  shade  of 
black.  The  property  of  combining  with  metallic  mordants  pos- 
sessed by  these  dyestuffs  is  due  to  the  presence  of  two  hydroxyl- 
groups  in  the  peri  position.  Chromotropes  2  R,  2  B,  and  6  B  give 
a  red  solution  with  concentrated  sulphuric  acid,  8  B  and  10  B  give 
a  blue  solution. 

Amidonaphtholsulphonic  Acids. 

Several  of  these  acids  are  known,  but  only  one,  the  7  or  G  acid, 
is  of  importance.  It  is  prepared  by  action  of  caustic  soda  on 
/3-naphthylaminedisulphonic  acid  Gr  (from  /3-naphtholdisulphonic 
acid  and  ammonia)  at  about  260°.  It  may  be  diazotised,  and 
reacts  with  diazo-compounds  to  produce  azo-colours,  which  may 
be  diazotised  and  combined  on  the  fibre  with  other  amines  and 
phenols.  (See  below,  under  Tetrazo-colours.) 

The  reaction  between  tetrazo-compounds  and  y-amidonaphthol- 
sulphonic  acid  may  be  effected  in  either  alkaline  or  slightly  acid 
solution,  and  the  products  differ  according  to  which  condition 
is  observed.  The  exact  reason  for  this  behaviour  has  not  been 
explained.  For  example,  in  the  preparation  of  diamine  blacks  R 
and  B,  and  diamine  blue-black  E,  the  combination  of  the  tetrazo- 
compound  with  ry-amidonaphtholsulphonic  acid  is  effected  in 
alkaline  solution,  while  in  the  cases  of  Diamine  Violet  and  Fast 
Red  a  slightly  acid  solution  is  used. 

P.  60.  The  following  Azo-dyes  contain  the  groups  necessary 
theoretically  for  the  formation  of  mordant-dyeing  colours.  In  fact 
they  yield  fast  shades  when  applied  in  conjunction  with  a  chromium 
mordant.  It  may  be  remarked  that  Diamond  Black  (p.  66)  belongs 
to  the  same  category. 


APPENDIX. 


291 


Dyestuff. 

Diazotised  Base, 

Combined  with 

Diamond  Yellow  G.  . 

M-amidobenzoic  acid. 

Salicylic  acid. 

Diamond  Yellow  R  .  . 

0-amidobenzoic  acid. 

Salicylic  acid. 

f 

1  mol.  salicylic  acid,  1  mol. 

Cloth  Brown  R    

Benzidine. 

a-naphtholsulphonic 

( 

acid. 

Cloth  Brown  G    
Cloth  Orange    

>                  1 

| 

1  mol.  salicylic  acid,  1  mol. 
/3/3-dioxynaphthalene. 
1  mol.  salicylic  acid,  1  mol. 

1 

resorcm. 

P.  66.  Several  black  dyes  of  the  disazo  class  have  recently 
appeared  in  commerce,  and  the  more  important  of  these  are  given 
here.  In  the  list  the  diazo-compound  of  the  first-named  body  is 
allowed  to  react  with  the  second,  and  the  resulting  amido-azo- 
compound  is  diazotised  and  combined  with  the  third  constituent. 

Blue-Black  B I  /3-uaphthylaminesulphonic  acid  +  a-naphthylamine  + 

I      /3-naphtholdisulphonic  acid  R. 

j  /3-naphthylamine-y-disulphonic  acid+a-naphthylamine 


Azo  Black 

NapUhol  Black  B  . . 

Naphthol  Black  3  B 
Naphthol  BlackQB. 


+R  acid, 
a-naphthylaminedisulphonic    acid     B  +  a-naphthyl- 

amine+R  acid, 
a-naphthylaminedisulphonic  acid  (Dahl)-j-a-naphthyl- 

amine-j-R  acid, 
a-naphthylaminedisulphonic    acid    B  +  a-naphthyl- 

amine+diphenylmetaphenylenediamine. 
Victoria  Black   .         .  \  SulPhanilic  acid  +  a-naphthylamine  +  1-8    dioxy- 
I     naphthalenesulphonic  acid. 


Neiu  Black 

Anthracite  Black 


P.  69.  a-Naphthylaminesulphonic  Acids. 

On  nitration  of  a-naphthalene-sulphonic  acid,  or  on  sulphonation 
of  a-nitronaphthalene,  a  mixture  of  two  acids  is  formed.  These 
are  separated  by  taking  advantage  of  the  different  solubilities  of 
their  sodium  salts  in  water. 

The  sparingly  soluble  sodium  salt  yields  an  a-naphthylamine- 
sulphonic  acid  on  reduction,  which  has  the  constitution  expressed 
by  the  formula : 

NH2 


SO.H 


292  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

It  is  known  as  naphthalidinesulphonic  acid  or  simply  as  Laurent's 
acid.  It  is  used,  but  not  to  any  great  extent,  in  the  manufacture 
of  azo-colours.  The  more  easily  soluble  sodium  salt  obtained  above 
yields  a-naphthylaminesulphonic  acid  S  (peri -acid)  on  reduction. 
It  has  the  constitution  : 

S03H      NH2 


It  has  hitherto  not  been  made  use  of  in  the  preparation  of 
azo-dyes. 

The  preparation  of  these  acids  is  described  in  British  Patents 
Nos.  15775  and  15782,  1885. 

The  Laurent  acid  is  also  formed  by  action  of  fuming  sulphuric 
acid  on  a-naphthylamine  hydrochloride  or  on  acet-a-naphthalide. 

a-Naphthylaminedisulphonic  Acids. 

Certain  of  these  acids  are  used  in  the  manufacture  of  black 
azo-colours.  A  mixture  of  acids  is  formed  by  sulphonation  of 
naphthionic  acid  with  fuming  sulphuric  acid,  and  these  are 
separated  by  treating  the  calcium  salts  of  the  mixture  with  alcohol. 
The  calcium  salt  soluble  in  alcohol  of  96  °/0  yields  acid  No.  I.,  the 
residue  contains  acids  II.  and  III.,  of  which  II.  is  soluble  in  alcohol 
of  85  %.  Acid  I.  yields  azo-colours  of  no  value,  and  No.  III.  is 
of  greater  importance  than  No.  II.  Germ.  Pat.  41957,  Sept.  4, 
1886. 

ft-Naphthylaminedisulphonic  Acids. 

These  acids  are  prepared  by  heating  the  corresponding  /3-naph- 
tholdisulphonic  acids  with  ammonia.  Thus  K  acid  yields  R-amido- 
acid  and  G-(7)-acid  yields  G-(y)-amido-acid.  The  G-amido-acid 
is  also  obtained  by  sulphonation  of  /3-naphthylamine  at  100-140° 
with  fuming  sulphuric  acid. 

a-Naphtholdisulphonic  Acids. 

I.  Schollkopf  acid. — a-naphthylaminesulphonic  acid  S  (suprh] 
is  sulphonated,  and  the  resulting  disulphonic  acid  converted  into 


APPENDIX, 


293 


naphtholdisulphonic  acid  by  the  diazo-reaction.     The  Schollkopf 
acid  has  the  constitution 

SO,H      OH 


SO8H 

(Brit.  P.  1885,  15775-15782).  It  is  used  in  the  manufacture  of 
azo-dyes. 

II.  a-naphtliol-e-disulplionic  acid  (Andresen  acid). — The  mixture 
of  disulphonic  acids  obtained  by  sulphonatioii  of  naphthalene  is 
nitrated  and  reduced.  The  sodium  salts  of  the  amidodisulphonic 
acids  obtained  are  treated  with  water.  The  more  easily  soluble 
salt  yields  the  Andresen  acid  by  the  diazo-reaction,  the  sparingly 
soluble  one  corresponds  to  the  Schollkopf  acid. 

The  Andresen  acid  has  the  constitution 


SO.H       OH 


S03H 


It  yields  azo-dyes  of  a  pure  bluish  shade,  and  is,  next  to  the 
Nevile-Winther  acid,  the  most  important  derivative  of  a-naphthol. 

A  peculiar  property  possessed  by  a-naphtholsulphonic  acids 
which  contain  hydroxyl-  and  sulpho-groups  in  the  peri  (1*8) 
position,  is  that  they  yield  anhydrides  by  elimination  of  water,  and 
these  anhydrides  (called  sultones)  are  frequently  obtained  in  place 
of  the  acids,  on  decomposing  the  diazo-compounds  with  boiling 
water.  Thus  the  naphtholsulphonic  acid  corresponding  to 
a-naphthylaminesulphonic  acid  S  yields  naphtho-sultone, 


SO 


294  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

The  Schollkopf  acid  gives  naphthosultone-sulphonic  acid, 

S02 O 


san 


while  an  isomer  is  obtained  from  the  Andre  sen  acid.  (Literature  : 
G.  Schultz,  Ber.  xx.  p.  3162 ;  H.  Erdmann,  Annalen,  ccxlvii. 
p.  344 ;  Bernsthen,  Ber.  xxii.  p.  3327  ;  Armstrong  &  Wynne, 
Proc.  Chem.  Soc.  1890,  p.  125.  Brit.  Patents,  1885,  15775- 
15782;  1888,4625,  5910.) 

Dioxynaphthalenesulphonic  Acids. 

Several  of  these  acids  are  used  in  the  manufacture  of  azo-colours. 

I.  Dioxynaphthalenemonosulphonic  acid  S  is  prepared  by 
melting  a-naphtholdisulphonic  acid  (Schollkopf)  with  caustic  soda, 
and  has  accordingly  the  constitutional  formula : 


OH 


S03H 


Azo-fuchsine  B.     Diazotoluene  and  dioxynaphthalenesulphonic 

Acid  S. 

Azo-fuchsine  G.     Diazobenzenesulphonic  acid  and  dioxy- 
naphthalenesulphonic Acid  S. 

These  two  dyestuflfs  dissolve  in  water  with  a  bluish-red  colour, 
and  in  concentrated  sulphuric  acid  with  a  violet  colour.  Azo- 
fuchsine  B  comes  into  commerce  as  a  brownish-black  powder, 
azo-fuchsine  G  as  a  reddish-brown  powder. 


APPENDIX. 


295 


They  produce  magenta  shades  on  wool  and  are  recommended  as 
substitutes  for  acid  magenta  on  account  of  their  fastness  to  light 
and  the  clearness  of  the  shades  obtained.  They  may  also  be  used 
for  printing  woollens  prepared  with  alum  and  stannic  chloride. 
German  Pat.  54116,  Oct.  25,  1889. 


Dioxynaphthalenedisulphonic  Acid  (Chromotrope  Acid). 

Naphthalene  is  sulphonated  with  fuming  sulphuric  acid  at  from 
80°-180°  according  to  the  strength  of  acid  employed.  The  tri- 
sulphonic  acid  obtained  has  the  constitution 


SO,H 


SO,H 


S03H 


It  is  nitrated  and  reduced,  and  the  resulting  amido-acid  submitted 
to  the  diazo-reaction  whereby  a-naphtholtrisulphonic  acid  or  its 
sultone  is  formed.  This  yields  a  dioxynaphthalenedisulphonic 
acid  (Chromotrope  Acid)  on  fusion  with  caustic  soda. 

The  chromotrope  acid  is  constituted  according  to  the  formula : 


OH 


S03H 


SOJJ 


Dyes  from  Benzidine  and  Analogous  Bases. 

In  the  Table  on  p.  72  several  derivatives  of  ethoxybenzidine  are 
enumerated,  and  the  reactions  whereby  this  base  is  obtained  are 
described  here.  Diazobenzene  chloride  reacts  with  j9-phenolsul- 
phonic  acid,  producing  benzene -azo-paraphenolsulphonic  acid,  the 
azo-chain  taking  up  an  ortho-position  with  regard  to  the  hydroxyl- 
group. 


296  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

Accordingly  the  compound  is  constituted  according  to  the 
formula : 

i       2  OH         1 

C6H5-N=N— C6H/U 

SO3H     4 

On  heating  with  ethyl  chloride  or  bromide  and  alcohol  in 
presence  of  alcoholic  potash,  an  ether  is  formed.  On  reduction 
with  stannous  chloride  or  zinc-powder  and  caustic  soda,  the  ether 
undergoes  an  intramolecular  change,  a  sulphonic  acid  of  ethoxy- 
benzidine, of  the  constitution  : 

4  1 1         /OC2H5      3 

NH2— C6H4— C6H2rS03H       6 

NH2         4 

is  formed.     This  is  heated  with  water  under  pressure  to  170°,  and 
sulphuric  acid  splits  off,  forming  ethoxybenzidine  sulphate. 

OC2H5 

Ethoxybenzidine  is  used  in  the  manufacture  of  a  number  of  the 
so-called  diamine  colours. 

Toluylenediaminesulphonic  acid  of  the  constitution 


NIL 


S03H 


may  be  diazotised.  The^  tetrazo-compound  reacts  with  amines 
and  phenols;  the  toluylene  browns  are  combinations  with  two 
molecules  of  a  metadiamine. 

In  the  Table  on  p.  74,  cotton-yellow  and  salmon-red  are 
erroneously  described  as  obtained  from  diamidodiphenylene. 
They  are  derivatives  of  diamidodiphenylurea,  but  are  prepared 
indirectly. 


APPENDIX. 


297 


Cotton-yellow  is  obtained  by  action  of  phosgene  on  two  molecules 
of  amidobenzene-azo- salicylic  acid,  and  has  the  formula : 

CO[NH-C6H4-N=N-C6H3 .  OH  .  COOH]2. 

Salmon-red  is  prepared  in  an  analogous  manner  from  amido- 
benzene-azonaphthionic  acid,  and  has  the  formula : 

CO[NH-C6H4-N=N-C10H5NH2 .  S03H]2. 

Mimosa  is  prepared  by  action  of  ammonia  on  the  diazo-compound 
of  primuline. 

Mikado  Colours. — The  yellow-orange  and  brown  dyestuffs  known 
under  this  designation  are  prepared  by  action  of  alkalies  on  para- 
nitrotoluenesulphonic  acid  in  presence  of  oxidizable  substances, 
such  as  arsenic  us  acid,  glycerine,  phenols,  tannic  acids,  &c.  Brit. 
Pat.  1888,  2664. 

They  are  probably  more  or  less  impure  azoxystilbenedisul- 
phonic  acids.  They  dye  cotton  directly  from  a  salt  bath  and 
give  moderately  fast  shades. 

The  following  Table  comprises  some  of  the  most  important 
direct  dyes  of  recent  introduction. 


Dyestuff. 

Diazotised  Base. 

Combined  with 

1  mol.  toluylene-diamine- 

Toluylene  Orange  .... 

Benzidine. 

sulphonic  acid. 
1    mol.    0-cresol-carbonic 

acid. 

Diamine  Scarlet  .... 

» 

2  mols.  /3-naphthol  y-disul- 
phonic  acid. 

1  mol.  phenol. 

Diamine  Scarlet  R  .  . 

I 

1  mol.  /3-naphthol  G-disul- 
phonic  acid.     The  pro- 

1 

duct  is  ethylated. 

( 

1   mol.  -y-amidonaphthol- 

Diamine  Brown  V  .  . 

• 

sulphonic  acid. 
1    mol.    m-phenylenedia- 

( 

mine. 

Thiazol  Yellow     ) 
Clayton  Yellow    f 

Dehydrothio  toluidine- 
sulphonic  acid. 

Dehydrothiotoluidinesul- 
phonic  acid. 

Congo  Brown  G  §•  R  are  prepared  by  action  of  diazotised  sul- 
phanilic  acid  and  naphthionic  acid  respectively  on  the  combination 


298  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

obtained  from  tetrazo-diphenyl  with  1  mol.  of  salicylic  acid  and 
1  mol.  of  resorcin. 

Diamine  Blue  6  G. — /3-naphthylaminedisulphonic  acid  diazo- 
tised  and  combined  with  1'2  amidonaphthol  ether.  The  product 
is  diazotised  and  combined  with  /3-naphthol. 

Benzo-grey. — Tetrazodiphenyl  is  combined  with  equal  molecules 
of  salicylic  acid  and  a-naphthylamine,  the  product  diazotised  and 
combined  with  a-naphtholsulphonic  acid  (Nevile  and  Winther) . 

Benzo-olive. — Is  prepared  similarly  to  the  above ;  dioxynaphtha- 
lenesulphonic  acid  S  being  substituted  for  the  last-named  com- 
ponent. 

Benzo-indigo-blue. — The  combination  of  benzidine  with  1  mol. 
a-naphthylamine  is  diazotised  and  combined  with  two  molecules 
of  dioxynaphthalenesulphonic  acid  S. 


OXYQUINONES  AND  QUINONE  OXIMES. 

P.  91.  Alizarin-blue  S  has   the  composition  expressed  by  the 
formula  : 

C17H9NO4  +  2NaHSO3 
(H.  Brunck  and  Graebe,  Ber.  1882,  vol.  xv.  p.  1783.) 


TRIPHENYLMETHANE  DYESTUFFS. 

P.  110.  Cyanine  B  is  prepared  by  oxidation  of  the  sulphonic 
acids  of  meta-oxytetralkyldiamidotriphenylcarbinol.  (Germ.  Pat. 
60961.) 

It  is  a  greenish-blue  dyestuff,  tolerably  fast  to  soap  and  light, 
and  recommended  as  a  substitute  for  indigo-extract. 

P.  112.  New  Magenta. — This  product  is  prepared  commercially 
by  the  synthetic  process  outlined  on  p.  112. 

Anhydroformaldehyde-aniline,  C6H6— N  =  CH2,  is  heated  with  a 
mixture  of  orthotoluidine  and  its  hydrochloride  to  100°.  Aniline 
splits  off,  and  diamido-ditolylmethane 


APPENDIX.  299 


NH 


is  formed.  On  further  heating  with  ortho-toluidine,  hydrochloric 
acid,  and  an  oxidising  agent,  a  third  molecule  of  ortho-toluidine 
enters  into  reaction,  the  "  new  magenta  "  being  produced.  It  is 
accordingly  a  salt  of  triamidotritolyl-carbinol, 


OH 

New  magenta  is  more  easily  soluble  than  ordinary  magenta,  and 
dyes  a  somewhat  bluer  shade. 

P.  128.  Diphenylamine  blue.  —  This  compound  has  long  been  con- 
sidered as  triphenylpararosaniline  identical  with  that  obtained  by 
phenylation  of  pararos  aniline.  Hausdorfer  (Ber.  xxiii.  p.  1961) 
has  compared  diphenylamine  blue  with  triphenylpararosaniline, 
and  demonstrated  their  identity. 

P.  130.  New  Green.  —  Is  analagous  to  Victoria-blue,  beiug  the 
condensation  product  of  dimethylamidobenzophenone  with  a- 
phenylnaphthylamine  (Germ.  Pat.  41756). 

The  commercial  product  is  a  paste.  It  is  principally  intended 
for  calico-printing,  and  gives  yellowish-green  shades. 

P.  138.  Aurotine  is  the  sodium  salt  of  tetranitrophenol- 
phthalem,  prepared  by  nitration  of  phenolphthalein  in  sulphuric 
or  acetic  acid  solution  (Eng.  P.  3441,  1889).  It  dyes  wool 
either  from  an  acid  bath  or  on  a  chromium  mordant,  pro- 
ducing orange-yellow  shades  fairly  fast  to  light  and  washing. 

P.  142.  Cyclamine.  —  On  heating  dichlorfluorescem  with  sodium 
sulphide  in  aqueous  solution,  a  thiodichlorfluorescem  is  formed. 
This  is  converted  into  a  tetraiodthiodichlorfluorescem  by  action 
of  iodine,  and  the  sodium  salt  appears  in  commerce  as  cycla- 
mine.  It  dyes  bluish-red  shades  resembling  those  obtained  with 
phloxine.  In  general  the  thio-derivatives  dye  bluer  shades  than 
the  corresponding  fluoresceins. 

P.  143.  Violamine  (Fast  acid  violet],  R  §•  .B  .—These  dyestuffs  are 


300  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

obtained  by  action  of  ortho-  and  para-toluidine  respectively  on 
fluorescein-chloride.     (Germ.  Pats.  49057,  53300,  1889.) 

The  Violamines  are  used  for  wool  and  silk,  and  give  shades 
fast  to  alkalies  and  light. 


QUINONEIMIDE  DYESTUFFS. 

P.  158.  Thionine  blue  G  0.  —  This  dyestuff  is  closely  allied  to 
methylene  blue,  and  its  constitution  is  expressed  by  the  formula  : 

^C6H3-N(CH3)2 

/S    /CH3 
C6H3  =  N^C2H5 

XC1 

It  is  prepared  by  oxidation  of  dimethylparaphenylenediamine- 
thiosulphonic  acid  (see  Methylene  Blue)  with  ethyl-methylaniline, 
and  boiling  the  resulting  insoluble  green  compound  with  zinc- 
chloride  solution.  A  leuco-compound  is  formed,  and  is  converted 
into  dyestuff  by  oxidation.  The  commercial  product  forms  a 
reddish-brown  powder. 

Toluidine  Blue.  —  This  body  is  also  an  analogue  of  methylene 
blue,  the  dimethylparaphenylenediamine-thiosulphonic  acid  being 
oxidised  with  ortho-toluidine.  The  hydrochloride  has  the  consti- 
tution expressed  by  the  formula  : 

C6H3-N(CH3)2 


C6H2  —  CH3 
^ 
NH  .  HC1 

The  commercial  product  is  the  sulphate  and  forms  a  dark  green 
powder,  easily  soluble  in  water  forming  a  bluish-violet  solution. 
In  dyeing,  toluidine  blue  gives  redder  shades  than  methylene 
blue. 

Methylene  Blue  N.  —  This  dyestuff  is  a  recent  member  of  the 
series,  and  is  obtained  from  ethyl  -ortho-toluidine  in  the  same 
manner  as  methylene  blue  from  dimethyl-aniline. 


APPENDIX.  301 


It  dyes  redder  shades  than  methylene  blue. 
Its  constitution  is  expressed  by  the  formula  : 

CH3 
C6H2—  NH  .  C2H5 


.  C2H5 

Cl 

Thiocarmine.  —  This  compound  is  a  sulphonic  acid  of  the 
methylene-blue  series,  and  is  obtained  from  ethylbenzylaniline- 
monosulphonic  acid.  Thiocarmine  is  an  acid  dyestuff  and  pro- 
duces very  pure  greenish  shades  of  blue  on  wool,  which  are,  how- 
ever, not  very  fast  to  light. 

(English  Patents,  4596  and  19065,  1890.) 

P.  161.  —  The  oxyindamines  and  oxyindophenols  (Fast  Blue, 
Gallocyanines,  &c.)  are  characterised  by  the  ease  with  which  they 
react  with  amines  of  the  fatty  and  aromatic  series,  and  certain 
compounds  resulting  from  such  reactions  have  appeared  in 
commerce. 

Cyanamines.  —  This  name  has  been  given  to  the  compounds 
resulting  from  the  action  of  ammonia  and  amines  in  presence  of 
an  oxidising  agent  on  Fast  Blue  E/.  (A  description  of  Fast  Blue 
K  or  Naphthol  Blue  occurs  on  p.  161.) 

Ammonia-cyanamine  has  a  greener  shade  than  the  original  fast 
blue  ;  the  dimethylamine-cyanamine  is  more  valuable  on  account 
of  its  pure  greenish-blue  shade. 

It  has  been  demonstrated  that  the  green  shades  of  fast  blue 
contain  one  of  these  cyanamines  ;  the  formation  of  which  results 
from  the  interaction  of  fast  blue  B,  with  the  dimethylparapheny- 
lenediamine  formed  during  the  reaction.  (Schlarb.  Chem.  Zeit. 
1891,  pp.  1281  and  1318;  Witt.  Ber.  1890,  xxiii.  p.  2247.) 

P.  165.  Delphine  Blue  and  Gallic  Indigo  are  sulphonic  acids  of 
compounds  obtained  by  heating  gallocyanine  with  aniline  and  analo- 
gous bases.  The  constitution  of  these  bodies  has  not  been  deter- 
mined ;  they  are  not  simple  anilides  of  gallocyanine,  as  a  carboxyl- 
group  splits  off  during  the  reaction. 

These  dyestuffs  are  employed  in  calico-printing,   giving  pure 


302  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

blue  shades  when  applied  with  chromium  acetate.     (Germ.  Pat. 
55942,  Sept.  27,  1889;  50999,  July  23,  1889.) 

Wool  Greys. — These  dyestuffs  are  obtained  by  action  of  aniline 
and  analogous  bases  on  the  condensation-products  of  nitroso- 
dimethyl-  and  diethyl- aniline  on  Schaeffer's  /3-naphtholsulphonic 
acid. 

AZINE  DYESTUFFS. 

Fast  Black. — The  commercial  product  bearing  this  name  is 
obtained  by  action  of  nitroso-dimethylaniline  on  meta-oxy- 
diphenylamine.  It  contains  the  groups  characteristic  both  of  the 
oxyindamines  and  the  azines.  It  is  a  basic  dyestuff,  and  is  fixed 
on  cotton  prepared  with  sumac  and  acetate  of  iron. 

Malta  Grey  and  Nigrisine  are  bodies  of  unknown  constitution 
prepared  by  heating  nitrosodimethylaniline  hydrochloride  in 
aqueous  or  alcoholic  solution. 

Methylene  Grey  is  a  similar  solution  obtained  by  oxidation  of 
dimethylparaphenylene  diamine. 

(German  Patent,  49446,  Feb.  2,  1889.) 


INDULINES  AND  NIGROSINES. 

The  simplest  Induline  o£  the  naphthalene  series,  rosinduline 
par  excellence,  is  formed  by  heating  benzene-azo-a-naphthylamine 
with  aniline  in  alcoholic  solution  under  pressure.  Rosinduline 
base  forms  reddish-brown  crystals,  M.P.  198°-199°.  Its  consti- 
tution is  expressed  by  the  formula  : 


Accordingly  the  compound  described  on  p.  205  is  a  phenyl-rosin- 
duline. 


APPENDIX. 


303 


On  heating  with  hydrochloric  acid,  rosinduline  yields  ammonia 
and  rosindulone,  a  compound  having  the  constitutional  formula : 


Some  of  the  sulphonic  acids  of  rosindulone  are  now  pre- 
pared commercially,  and  come  into  commerce  as  Eosindulines. 

Rosinduline  2  B  dyes  wool  bluish  red  from  an  acid  bath. 

Rosindulines  2  G  and  G  produce  orange-red  and  scarlet  shades 
respectively,  and  when  dyed  on  silk  exhibit  a  fine  yellow 
fluorescence. 

On  heating  benzene-azo-a-dinaphthylamine  with  aniline,  naph- 
thyl  and  isonaphthylrosindulines  are  formed. 

Isonaphthylrosinduline  has  the  constitution  expressed  by  the 
formula : 


N.C6H5 
An  anilide  of  isonaphthylrosinduline  having  the  formula 


CHN 


.  CH 


N 


5, 


is  formed  along  with  phenylrosinduline  when  benzene-azo-a-naph- 
thylamine  is  heated  with  aniline. 

Naphthyl  blue  is  probably  a  salt  of  a  sulphonic  acid  of  amido- 
isonaphthylrosinduline,  and  naphthyl  violet  is  a  dyestuff  of  similar 
character.  They  are  principally  intended  for  silk,  on  which  they 
show  a  red  fluorescence. 

(O.  Fischer  and  E.  Hepp,  Annal.  cclxii.  pp.  237-264;  H.  v. 
Perger,  Mittheil.  Techn.  Gewerbemuseums,  1891,  pp.  202-253.) 


304  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 


INDIGO. 

A  process  in  the  preparation  of  indigo  from  the  plant  consists 
in  macerating  the  plants  in  water  and  subjecting  the  liquor  to 
the  action  of  air  in  presence  of  ammonia.  This  "ammonia 
process "  is  said  to  give  larger  yields  and  a  product  of  greater 
purity. 

Diacetylindigo. 

On  heating  indigo  blue  with  acetic  anhydride,  sodium  acetate, 
and  zinc  powder,  a  diacetylindigo  white  is  obtained.  On  oxidation 
with  nitrous  acid  in  presence  of  acetic  acid,  diacetylindigo  blue  is 
formed.  This  compound  forms  small  glittering  red  crystals,  soluble 
in  benzene  with  a  beautiful  red  colour.  Its  constitution  is  ex- 
pressed by  the  formula : 

/CO\  P/C°\r    TT 

6  4X  N  A  -  K  isr  A*11*  • 

XC2H30     1N  \C2H30 


Indigo disulphonic  Acid. 

The  mechanism  of  the  reactions  involved  in  the  synthetic  process 
for  preparing  this  compound  has  been  explained  by  Heymann 
(Berl.  Ber.  1891,  p.  3066).  The  yellow  solution  resulting  from  the 
action  of  the  sulphuric  anhydride  on  phenyl-glycine  contains  the 
sulphonic  acid  of  indoxyl-sulphuric  ester.  On  dilution  of  this 
solution,  oxidation  is  effected  by  the  sulphuric  anhydride. 


QUINOLINE  AND  ACRID  INE  DYESTUFFS. 

Berberine. 

Extensive  researches  on  the  constitution  of  berberine  have  been 
made  by  W.  H.  Perkin,  Jun.  (Chem.  Soc.  Journal,  1890,  p.  991). 
Berberine  is  allied  to  papaverine,  hydrastine,  and  narcotine  ;  it  is 
a  derivative  of  isoquinoline,  and  has  probably  the  constitution 
expressed  by  the  formula  : — 


APPENDIX.  305 

GIL .  O— C 


CH30—  C 

C 

( 

C 

XCH 

L 

1 
?       C 

CH 

fl—  C     V 

^cx  x( 

}( 

HC 

1 

C 

N       ( 

}H2 

\    , 

c 

/ 

V  ^c7 

H 

H       H 

On  oxidation  with  potassium  permanganate,  berberine  yields  the 
following  series  of  compounds,  all  containing  the  twenty  carbon 
atoms  of  berberine  intact : — 

Oxyberberine,  M.P.  198-200° C20H17NO4. 

Dioxyberberine  C20H17NO6. 

Berberal,  M.P.  149° C20H17NO7. 

Anhydroberberic  acid,  M.P,  237°    C20H17NO8. 

Berberic  acid,  M.P.  177-182°  C20H17NO9. 


DYESTUFFS  OF  UNKNOWN  CONSTITUTION. 

Patent  Fustine. 

Some  compounds  bearing  this  name  have  appeared  in  commerce. 
They  are  prepared  by  action  of  diazo- compounds  on  a  decoction 
of  fustic.  They  are  applied  in  the  same  manner  as  fustic. 

Fisetin,  Quercitin,  and  Rhamnetin. 

Herzig  (Monatsheite  f.  Chem.  1891,  pp.  172,  177)  has  demon- 
strated that  a  close  relationship  exists  between  these  compounds, 
and  the  formulae  given  on  pages  254-256  have  to  be  modified.  The 
molecular  weight  of  quercitin  was  determined,  and  from  this  and 
analytical  data  the  formula  for  quercitin  appears  to  be  C15H10O7. 
Rhamnetin  is  a  monomethylquercitin.  Quercitin  is  a  hydroxy- 
fisetin,  and  the  formula  proposed  by  Schmid  for  fisetin  has  to  be 
altered  according.  Analyses  of  fisetin,  its  acetyl,  methyl,  and 
ethyl  derivatives  prove  that  the  correct  formula  is  C15H10O5.  On 
oxidation  by  air  in  alkaline  solution,  fisetin  yields  resorcin  and 

x 


306  CHEMISTRY  OF  ORGANIC  DYESTUFFS. 

protocatechuic  acid,  while  quercitin  under  similar  conditions 
yields  phloroglucin  and  protocatechuic  acid,  these  results  being  in 
accordance  with  the  idea  that  quercitin  is  a  hydroxyfisetin. 

Orce'in. 
(Zulkowski  &  Peters,  Monats.  f.  Chem.  1890,  p.  227.) 

A  study  of  the  process  by  which  orcei'n  is  formed  from  lichens, 
by  action  of  ammonia  and  air,  shows  that  three  colouring-matters 
are  formed,  viz.,  orcein,  a  yellow  crystalline  compound,  and  an 
amorphous  body  resembling  litmus. 

Pure  crystallised  orcein  is  insoluble  in  water,  ether,  and  benzene  ; 
soluble  in  alcohol,  acetone,  and  acetic  acid.  Pure  orcein  possesses 
nearly  two  hundred  times  the  tinctorial  power  of  orchil  extract. 

The  composition  of  orcein  is  expressed  by  the  formula 
C28H24N2O7,  an(i  its  formation  may  be  expressed  by  the  equation 

4  C7H8O2  +  2NH3  +  60  =  C28H24N2O7  +  7H3O. 

The  yellow  compound  has  the  formula  C21H19N05,  and  is  prob- 
ably formed  according  to  the  equation 


It  was  found  that  the  formation  of  orcein  from  orcin  is  much 
more  rapid  in  presence  of  hydrogen  peroxide ;  other  oxidising 
agents  did  not  give  favourable  results. 

No  compound  of  the  orcein  class  can  be  obtained  from  resorcin 
by  action  of  hydrogen  peroxide  and  ammonia.  From  a  mixture 
of  resorcin  and  orcin  a  mixed  orcein,  "  Reso-orcein,"  C20H20N2O7, 
is  formed. 


ALPHABETICAL    INDEX. 


ACID  dyes,  14. 
Acridine  dyes  tuffs,  207. 

orange,  216. 

yellow,  216. 

Aldehyde  green,  128. 
Alizarin,  82. 

,  Alkyl-,  83. 

black,  81. 

blue,  91. 

blue  OR,  90. 

-  blue  S,  298. 

Bordeaux,  89. 

brown,  89. 

— ,  Ohloro-,  83. 

—  cyanine,  89. 

dyeing,  86. 

green  S,  92. 

-  indigo  blue  S,  92. 

,  Nitro-,  87. 

orange,  87. 

-  red  S,  83. 

sulphonic  acid,  83. 

synthesis,  83. 

yellow,  61,  245. 

Alkannin,  263. 
Amaranth,  56. 
Amidoazobenzene,  35. 
— ,  Acetyl-,  37. 

/3-naphtholdisulphonic     acid 
55. 

disulphonic  acid,  36. 

monosulphonic  acid,  36. 

Amidoazonaphthalene,  43. 
Amidoazotoluenebenzene,  39. 
Amidoazotoluenes,  39. 
Amidoazoxylenes,  40. 
Amidonaphtholsulphonic  acids,  290. 
Amidooxyazobenzene,  46. 
Annatto,  258. 
Anthracene  yellow,  92. 
Anthracite  black,  291. 
Anthraflavic  acid,  89. 
Anthragallol,  89. 


Anthrapurpurin,  88. 
Anthraquinoline,  91. 
Anthraquinone,  84. 
—  ,  Dichloro-,  84. 

-  disulphonic  acids,  84. 

-  dyes,  81. 

-  monosulphonic  acid,  84. 
Archil,  260. 

-  brown,  65. 
Auramine,  98. 
Aurantia,  26. 
Aurin,  132. 

Aurin-tricarbonic  acid,  134. 
Aurotine,  299. 
Auxochromic  groups,  13. 
Azarin  S,  75. 

Azine  dyes,  169. 
Azine-green,  189. 
Azoaniline,  41. 
Azobenzeneazoparacresol,  66. 
Azobenzenedimethylamidobenzoic  -  acid, 

uU* 
Azobenzene-a-naphthol,  53. 

-    monosulphonic  acid,  54. 
Azobenzene-jft-naphthol,  54. 

—  disulphonic  acids,  55. 

—  monosulphonic  acids,  54. 
Azobenzene  salicylic  acid,  61. 
Azo-black,  291. 

Azo-blue,  71,  73. 

Azo-carmine,  205. 

Azo-cornpounds,  28. 

Azodibenzenephenylenediamine,  65. 

Azodibenzenetoluylenediamine,  66. 

Azo  -  d  -  diamidobenzoic    acid-y-benzene- 

sulphonic  acid,  60. 
Azo-des  application,  34. 


-  from  amidoazo-compounds,  63. 

-  from  benzidine,  68. 
—  manufacture,  34. 

-  on  fibre,  77. 
Azofuchsine,  294. 
Azonaphthalene  /3-naphthol,  57. 

-  disulphonic  acids,  58. 


308 


INDEX. 


Azonaphthalene  inonosulphonic  acid,  57. 

—  resorcin,  46. 

salicylic  acid,  61. 

Azoorseilline,  72. 
Azophenine,  201. 
Azophenols,  45. 
Azorubine,  58. 
Azoviolet,  74. 
Azyline,  42. 

B. 

Basic  dyes,  14. 
Basle  blue,  188. 
Benzaurine,  135. 

Benzeneamidoazouaphthalene,  43. 
Benzenedisazobenzene  /3-naphthol,  64. 

—  disulphcnic  acid,  64. 

—  raonosulphonic  acid,  64. 
Benzenetetrazobeuzenephenol,  63. 
Benzhydrol,  97. 

Benzidine  blue,  72. 
Benzoazurines,  73,  74. 
Benzo-black,  74. 
Benzo-blue-black  G  &  E,  74. 
Benzo-brown  B,  74. 
Benzoflavine,  216. 
Benzo-grey,  298. 
Benzoindigo-blue,  298. 
Benzo-olive,  298. 
Benzo-orange,  72. 
Benzopurpurines,  72,  73. 
Berberine,  212,  304. 
Bismark  brown,  42. 
Bixin,  258. 
Black,  Alizarin,  81. 

,  Aniline,  192. 

dyeing,  197. 

,  Anthracite,  291. 

,  Azo,  66, 295. 

,  Benzo-,  74. 

— ,  Benzo-blue,  74. 
,  Brilliant,  66. 

— ,  Diamine,  E,  72,  290. 

— , ,  B,  73,  290. 

— ,  — ,  Blue  E,  73,  290. 

— ,  Diamond,  66. 
,  Fast,  302. 

— ,  Jet,  E,  66. 

— ,  Naphthol,  291. 

— ,  Naphthylamine,  D,  66. 

—  New,  291. 
,  Victoria,  291. 

— ,  Wool,  65. 
Blue,  Alkali,  127. 

— ,  Aniline,  126. 

— ,  Azo,  71,  73. 
,  Basle,  188. 

— ,  Benzidine,  72. 
-  black  B,  295. 

,  Cotton,  127. 

,  Delphine,  300. 

— ,  Diamine,  73,  298. 


Blue,  Diphenylamine,  128,  299. 

,  Fast,  161. 

.  Gallamine,  164. 

— ,  Meldola,  162. 

,  Methylene,  155,  300. 

,  Naphthol,  161. 

,  Naphtyl,  303. 

,  Night,  127. 

,  Nile,  163. 

,  Paraphenylene,  203. 

,  Phenylene,  149. 

,  Eesorcin,  167. 

— ,  Toluidine,  300. 

,  Toluylene,  150. 

,  Victoria,  130. 

,  Water,  127. 

Bordeaux,  56,  57. 

-  B,  58. 

extra,  72. 

Brazilein,  253. 
Brazilin,  252. 
Brilliant  azurine  5  Gr,  74. 
black,  66. 

Congo,  72. 

-  purpurin,  73. 
Brown,  Archil,  65. 

,  Benzo,  74. 

,  Bismark,  42. 

,  Cloth,  291. 

• ,  Congo,  297. 

,  Diaruine,  297. 

,  Toluylene,  296. 


C. 

Cachou  de  Laval,  271. 
Canarine,  247. 
Carmine-red,  266. 
Carminic  acid,  265. 
Carminnaphthe,  58. 
Carotin,  260. 
Carthamin,  262. 
Catechin,  271. 
Catechu,  270. 

tannic  acid,  271. 

Chinese  green,  264. 
Chrome  violet,  134. 
Chromogens,  3. 
Chromophors,  3. 
Chromotropes,  289. 
Chrysamine  G,  71,  72. 

E,  72. 

Chrysanilines,  124,  212. 
Chrysin,  259. 
Chrysoidine,  40. 
Chrysophenine,  74. 
Cbrysotoluidine,  124. 
Citronine,  39. 
Classification,  21. 
Cloth  brown,  291. 


INDEX. 


309 


Cloth  orange,  291. 
Coccinines,  56,  57,  267. 
Cochineal,  265. 
Colour,  1. 
Ccerulein,  144. 
Congo  red,  68,  72. 

,  Brilliant,  G,  72. 

Corinth,  72. 

violet,  72. 

Crocetin,  264. 
Crocin,  264. 
Crude  products,  20. 
Cumeneazoresorcin,  45. 
Curcumin,  259. 
Cyanamines,  300. 
Cyanine,  203. 

B,  298. 

Cyanosine,  142. 
CycJamine,  299. 


D. 


Dehydrothiotoluidine,  75. 
Delphine  blue,  300. 
Deltapurpurin,  72,  73. 
Developers,  76. 
Diaruidoazobenzene,  40. 
Diamidoazotoluenes,  42. 
Diamond  yellow,  291. 
Dichroines,  165. 
Diisatogen,  224. 
Dimethylamidoazobenzene,  37. 

sulphonic  acid,  37. 

Dinaethylamidobenzeueazobenzoic      acid 

59.     ' 
Dimethylamidobenzoic      acid-azobenzoic 

acid,  60. 

Dinitrocresol,  24. 
Dinitronaphthol,  25. 

—  sulphonic  acid,  25,  289. 
Dinitrosoresorcin,  93. 
Dioxindol,  221. 
Dioxyazobenzenes,  44,  45. 

sulphonic  acid,  45. 

Dioxy naphthalene  sulphonic  acids,  294. 
Dioxynaphthoquinone,  81. 
Dioxy tartaric  acid,  101. 
Diphenylamine  blue,  128,  299. 
Diphenylrosaniline,  126. 
Disazo  dyestuffs,  62. 
Dyeing  (theories),  3. 


Ellagic  acid,  245. 
Eosin,  139. 

ether,  140. 

— •  scarlet,  141. 
Erica,  76. 


Erythrosin,  141. 
Ethoxybenzidine,  296. 
Eupittonic  acid,  133. 
Eurhodines,  172. 
Eurhodoles,  175. 
Euxanthic  acid,  243. 
Euxanthone,  243. 


F. 

Fisetin,  254,  305. 
Flavaniline,  210. 
Flavin,  254. 
Flavopurpurin,  88. 
Fluorescein,  139. 
— ,  Tetrabrom-,  139. 

,  Tetrabromodichlor-,  142. 

,  Tetrabromotetrachlor-,  142. 

,  Tetraiodo-,  141. 

Fluorescent  blue,  167. 
Fluorindine,  206. 
Fuchsine,  118. 
Fustic,  253.  ' 

,  Young,  254. 

Fustine,  305. 

G. 

Gallacetophenone,  245. 
Gallamine  blue,  165. 
Gallein,  144. 
Gallic  indigo,  300. 
Gallocyanine,  163. 
Galloflavine,  246. 
Gambine,  95. 
Girofle,  185. 
Glycereins,  145. 
Green,  Acid,  110. 

— ,  Aldehyde,  128. 

,  Azine,  189. 

,  Azo,  116. 

,  Benzaldehyde,  107.     / 

,  Bindschedler's,  149.  / 

,  Brilliant,  109. 

,  Chinese,  264. 

,  Ethyl,  109. 

,  Fast,  94. 

,  Helvetia,  109. 

,  Iodine,  122. 

,  Light,  110. 

,  Malachite,  107. 

,  Methyl,  116. 

,  Methylene,  161. 

,  Naphthol,  95. 

,  New.  299. 

— ,  New  solid  3  B,  109. 

, Victoria  3  B,  109. 

,  Quinoline,  110. 

,  Solid,  109. 

,  Victoria,  109. 


310 


INDEX. 


Grey,  Fast,  271. 

,  Methylene,  302. 

,  Wool,  302. 


H. 

Hsematein,  250. 
Hsematoxylin,  260. 
Helianthine,  38. 
Heliotrope,  74. 

Hexaethylpararosaniline,  116. 
Hexamethoxylaurin,  133. 
Hexamethoxylpararosaniline,  134. 
Hexametkylpararosaniline,  115. 
Hexamethyl-rosaniline,  122. 
Hexanitrodiphenylamine,  26. 
History,  17. 
Hydrazides,  96. 


I. 

Imidothiodiphenylimide,  158. 
Indarnines,  146,  149. 
Indazine  M,  188. 
Indian  yellow,  242. 
Indiglucine,  225. 
Indigo,  219. 

,  ammonia  process,  304. 

,  application,  228. 

blue,  224. 

carmine,  227. 

,  Ohloro-,  226. 

,  Diacetyl,  304. 

,  Dibenzoyl,  226. 

dicarbonic  acid,  229. 

extract,  227. 

purpurin,  230. 

red,  230. 

rubin,  230. 

substitute,  251. 

—  sulphonic  acids,  227,  304. 

,  synthesis,  231. 

white,  226. 

Indigotin,  225. 
Indoine,  229. 
Indol,  219. 
Indophenine,  222. 
Indophenols,  151. 
Indoxanthic  ether,  224. 
Indoxyl,  220. 
Indoxylic  acid,  221. 
Induliues,  200,  302. 

,  application,  204. 

,  soluble,  203. 

Isatic  acid,  223. 
Isatin,  222. 
Isatogenic  ether,  224. 
Isopurpuric  acid,  27. 
Isopurpurin,  88. 


K. 


Ketone-imides,  96. 


Laccaic  acid,  269. 
Lac-dye,  269. 
Lacmoid,  168. 
Lakes,  15. 
Lanuguinic  acid,  5. 
Leuco-compounds,  2. 
Litmus,  261. 
Logwood,  250. 
Lokaetin,  265. 
Lokain,  264. 
Lo-Kao,  264. 
Lutecienne,  141. 
Luteolin,  257. 


M. 

Maclurine,  253. 
Magenta,  118. 

,  Acid,  121. 

1  New,  298. 

residues,  124. 

S,  121. 

Mauvaniline,  124. 
Mauveine,  190. 
Mikado  colours,  297. 
Mimosa,  297. 

Monophenylrosaniline,  125. 
Mordant-dyeing,  15,  80. 
Morin,  253. 
Murexide,  248. 
Muscarine,  162. 


Naphthaquinoneoximes,  94. 

Naphthazarin,  81. 

Naphthol-azo-dyes,  46. 

Naphthol  black  B,  2B,  6B,  291. 

a  Naphtholmonosulphonic   acid,   Nevile 

and  Winther,  49. 

,  Schaefler,  49. 

a  Naphtholdisulphonic  acid,  Schollkopf, 

50,292. 

-  e,  275. 

trisulphonic  acid,  289. 

(3  Naphtholazobenzoic  acid,  59. 

3  Naphthol  disulphonic  acid  Q-,  52. 

d,  53. 

E,  53. 

—  monosulphonic  acid  crocein,  51. 

F,  52. 

Schaeffer,  52. 

Naphthol  yellow,  25,  289. 


INDEX. 


311 


a  Naphtho-Sultone,  293. 
a  Naphthylamine  disulphonic  acids,  292. 
monosulphonic  acids,  69,  291. 

Phenylamidoazobenzene,  38. 
—  sulphonic  acid,  38. 
Phenylhydrazicles,  100. 

/3  Naphthylamine  disulphonic  acids,  292. 
monosulphonic  acids,  291. 

Phloxine,  142. 
Phthaleins,  136. 

Naphthyl  blue,  303. 
Neutral  dyes,  14. 

Phthalopheuones,  137. 
Picramic  acid,  27. 

New  black,  291. 

Picric  acid,  24. 

Nigrisine,  302. 

Pittacal,  133. 

Nigrosine,  200. 

Polchromine,  76. 

Nitrobroinsalicylic  acid,  26. 

Ponceaux,  56,  57. 

Nitre-compounds,  23. 

Primrose,  141. 

Nitrosonaphthols,  94. 

Primuline,  75. 

Printing,  16. 
Prune,  164. 

Purple,  Ethyl,  116. 

O. 

,  xiessian  JM,  /-t. 

Purpuriue,  87. 

Orange,  Acridine,  216. 

,  Benzo-,  B,  4  B,  6  B,  10  B,  72,  73. 

,  Benzo-,  G  &  E,  72. 

,  Brilliant,  73. 

,  Crocein,  55. 

—  ,  Delta-,  5  B  &  7  B,  72,  73. 

G-,  55. 

Purree,  242. 

1,  54. 

Pyronines,  143. 

II,  54. 
Ill,  38. 

Pyrophthalone,  209. 

IV,  38. 

,  Palatine,  26. 

,  Toluylene,  G  &  E,  73. 

Q. 

Orcein,  261,  306. 

Orchil  substitute,  43. 

Quercitin,  255,  305. 

Orcin,  261,  306. 

Quercitrin,  254. 

Orcirufamin,  168. 

Quinoline  dyes,  207. 

Orcirufin,  168. 

Quinone-imides,  146. 

Orseilline,  43. 

oximes,  80. 

Oxazines,  161. 

Quinophthalon,  209. 

Oxindol,  221. 

Oxy-azobenzene,  44. 

Oxy-azobenzenetoluene,  45. 

E. 

Oxyazo-compounds,  44. 

Oxyindamines,  161. 
Oxyindophenols,  161. 

Eed,  Anisol,  57. 
,  Carmine-,  266. 

Oxyketone  dyes,  245. 
Oxyquinones,  80. 
Oxythiodiphenylimide,  159. 

—  ,  Congo,  68,  72. 
,  Cotton,  73. 
,  Diamine,  3B,  73. 

,  NO,  73. 

,  Fast,  72. 

P. 

-,  Direct,  73. 

,  Fast,  57. 

Pararosaniline,  111. 

,  Magdala,  189. 

Pararosolic  acid,  132. 

,  Methylene,  160. 

Pen  tarn  ethylpararosaniline,  115 

,  Naphthylene,  74. 

Pentamethylrosaniline,  122. 

,  Phenetol,  57. 

Pentoxy-anthraquinone,  90. 

,  Quinoline,  208. 

Phenazine,  169. 

,  St.  Denis,  74. 

Phenolazo-meta-beuzoic  acid,  59. 

,  Salmon,  74,  297. 

Phenoldisazobenzene,  62. 

,  Silk,  59. 

Phenolphthalein,  138. 
Phenosaffranine,  178,  181. 

,  Toluylene,  175. 
Eesazurin,  167. 

,  Diazo-,  182. 

Eesorcinazobenzoic  acid,  59. 

,  Ethyl-,  183. 

Eesorcin-benzein,  135. 

,  Methyl-,  183. 

Eesorcindisazobenzene,  63. 

312 


INDEX 


Kesorufamine,  168. 
Kesorufin,  165. 
Ehamnetin,  256,  305. 
Ehodamine,  142. 

S,  143. 

Eoccelline,  57. 
Eosamine,  135. 
Eosaniline,  118. 

,  Acetyl,   123. 

aldehyde  compounds,  123. 

-  base,  120. 

benzoyl,  123. 

,  DiphenyJ,  126. 

dyes,  105. 

,  Hexamethyl,  122. 

,  Monophenyl,  125. 

,  Pentamethyl,  122. 

sulphonic  acids,  121. 

,  Tetrabroin-,  121. 

— ,  Tetraethyl,  122. 

,  Tetramethyl,  122. 

tribenzyl-methyliodide,  123. 

,  Triethyl,  123. 

,  Trirnethyl,  122. 

— ,  Triphenyl,  126. 
Eosazurines,  73. 
Eose  Bengal,  142. 
Eosindulines,  205,  303. 
Eosolic  acid,  133. 

-  dyes,  132. 
Euberythric  acid,  82. 
Eubramine,  185. 
Euficoccin,  267. 
Eutin,  256. 

S. 

Saifranine,  177. 

,  Pheno-,  178,  181. 

,  Tolu-,  185. 

Saffranol,  187. 
Saffron  substitute,  24. 
Saffrosine,  141. 
Santalin,  263. 
Scarlet,  Biebrich,  64. 

,  Brilliant,  59. 

,  Brilliant  Crocein  M,  65. 

,  Crocein,  3  B  &  7  B,  65. 

,  Crystal,  58. 

,  Diamine,  297. 

2  G,  55. 

,  Silk-,  59. 

Styrogallol,  92. 
Sulphonazurine,  73. 
Sun  Gold,  26. 
Yellow,  75. 


T. 


Tannin  lakes,  16. 
Tartrazine,  100. 


Tetraethylrosaniline,  123. 
Tetramethyldiamidobenzophenone,  96. 

chloride,  97. 

Tetramethyldiamidotriphenylcarbinol, 

106. 

,  Chlor-,  109. 

,  Nitro-,  108. 

sulphonic  acid,  109. 

Tetramethylpararosaniline,  114. 
Tetramethylrosaniline,  122. 
Tetranitrodiphenol,  26. 
Tetranitronaphthol,  26. 
Tetrazo-dyes,  62. 
Thiazines,  153. 
Thiocarmine,  301. 
Thiodiphenylamine,  153. 
Thioflavine,  76,  77. 
Thionine,  155,  300. 
Thionol,  159. 
Thionoline,  159. 
Thiotoluidine,  75. 
Toluidine  blue,  300. 
Toluylenediaminesulphonic  acid,  296. 
Toluylene  orange,  297. 
Triamidoazobenzene,  42. 
Triamidotriphenylcarbinol,  111,  118. 
Tribenzylrosaniline-methyliodide,  123. 
Triethylrosaniline,  123. 
Trimethylrosaniline,  122. 
Trinitroeuxanthone,  244. 
Trinitrophenol,  24. 
Trioxyacetophenone,  245. 
Trioxy-anthraquinone,  87. 
Trioxybenzophenone,  245. 
Tripheny  1m  ethane  dyes,  102. 
Triphenylrosaniline,  126. 

—  sulphonic  acids,  126, 127. 
Tropaolin  II  &  OO,  38. 

Y&0,44. 

OOONo.  1,  54. 

Turkey  red,  86. 
Turmeric,  260. 
Tyrian  purple,  269. 


V. 

Valuation  of  dyestuffs,  15. 
Yesuvine,  42. 
Yictoria-black,  291. 

blue,  130. 

green,  109. 

yellow,  24. 

Violamine,  299. 
Violaniline,  124. 
Yiolet,  Acid,  114. 

,  Amethyst,  185. 

,  Azo-,  74. 

,  Chrome-,  135. 

,  Congo,  72. 

,  Crystal-,  115. 

,  Diamine,  N,  72. 


INDEX. 


313 


Violet,  Hessian,  74. 

,  Hofmann's,  123. 

,  Lauth's,  155. 

,  Methyl-,  112. 

— ,  Neutral-,  176. 
,  Toluylene-,  176. 

X. 

Xanthorhamnin,  256. 


Y. 

Yellow,  Acid,  36. 
,  Acridine-,  216. 


Yellow,  Alizarin,  61. 
, ,  A  &  G,  245. 

,  Brilliant-,  26,  74. 

,  Carbazol,  74. 

— ,  Congo  paste,  72. 
,  Cotton-,  74,  297. 

— ,  Diamine,  N,  73. 

— ,  Fast-,  36. 

,  Hessian,  74. 

,  Indian,  39. 

,  Marti  us,  25. 

,  Metanil,  38. 

,  Naphthol,  8,  25,  289. 

,  Quinoline,  209. 

,  Salicyl-,  26. 

,  Sun,  75. 


FEINTED  BY  TAYLOR  AND  FRANCIS,  RED  LION  COURT,  FLEET  STREET. 


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8.  1933 


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UNIVERSITY  OF  CALIFORNIA